U.S. patent application number 11/952711 was filed with the patent office on 2008-03-27 for voltage generating apparatus, current generating apparatus, and test apparatus.
This patent application is currently assigned to Advantest Corporation. Invention is credited to Hiroki Andoh, Hironori Tanaka.
Application Number | 20080074133 11/952711 |
Document ID | / |
Family ID | 38872938 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080074133 |
Kind Code |
A1 |
Andoh; Hiroki ; et
al. |
March 27, 2008 |
VOLTAGE GENERATING APPARATUS, CURRENT GENERATING APPARATUS, AND
TEST APPARATUS
Abstract
There is provided a voltage generating apparatus that outputs a
power source voltage from a voltage outputting terminal. The
apparatus includes a voltage outputting section that outputs the
power source voltage according to a current or voltage to be input,
a first differential amplification section that compares the power
source voltage and a preset first reference voltage to output a
first control current or voltage reducing the power source voltage
output from the voltage outputting section when the power source
voltage is larger than the first reference voltage and output the
first control current or voltage raising the power source voltage
output from the voltage outputting section when the power source
voltage is smaller than the first reference voltage, a current
detector that detects a detecting voltage according to a power
source current output from the voltage outputting terminal, a
second differential amplification section that compares the
detecting voltage detected from the current detector and a second
reference voltage to output a second control current or voltage
reducing the power source voltage when a value obtained by
subtracting the second reference voltage from the detecting voltage
is larger, an addition section that inputs a current or voltage
obtained by adding the first control current or voltage and the
second control current or voltage into the voltage outputting
section, and a third differential amplification section that
supplies a voltage obtained by amplifying a difference voltage
obtained by subtracting the detecting voltage from a preset third
reference voltage to the second differential amplification section
as the second reference voltage.
Inventors: |
Andoh; Hiroki; (Tokyo,
JP) ; Tanaka; Hironori; (Tokyo, JP) |
Correspondence
Address: |
OSHA LIANG L.L.P.
1221 MCKINNEY STREET
SUITE 2800
HOUSTON
TX
77010
US
|
Assignee: |
Advantest Corporation
Tokyo
JP
179-0071
|
Family ID: |
38872938 |
Appl. No.: |
11/952711 |
Filed: |
December 7, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11475577 |
Jun 27, 2006 |
|
|
|
11952711 |
Dec 7, 2007 |
|
|
|
Current U.S.
Class: |
324/750.01 ;
324/764.01 |
Current CPC
Class: |
G01R 31/2839
20130101 |
Class at
Publication: |
324/763 |
International
Class: |
G01R 31/02 20060101
G01R031/02 |
Claims
1-5. (canceled)
6. A test apparatus that tests a device under test, comprising: a
current generating apparatus that outputs a power source current to
be supplied to the device under test from a current outputting
terminal; and a test processing section that tests the device under
test in a state that said current generating apparatus has supplied
the power source current to the device under test, wherein said
current generating apparatus comprises: a current outputting
section that outputs the power source current according to a
current or voltage to be input; a current detector that detects the
power source current output from the current outputting terminal; a
fourth differential amplification section that compares the power
source current and a preset first reference current to output a
first control current or voltage reducing the power source current
output from said current outputting section when the power source
current is larger than the first reference current and output the
first control current or voltage raising the power source current
output from said current outputting section when the power source
current is smaller than the first reference current; a fifth
differential amplification section that compares a power source
voltage at the current outputting terminal and a second reference
voltage to output a second control current or voltage reducing the
power source current when a value obtained by subtracting the
second reference voltage from the power source voltage is larger;
an addition section that inputs a current or voltage obtained by
adding the first control current or voltage and the second control
current or voltage into said current outputting section; and a
sixth differential amplification section that supplies a voltage
obtained by amplifying a difference voltage obtained by subtracting
the power source voltage from a preset third reference voltage to
said fifth differential amplification section as the second
reference voltage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a voltage generating
apparatus, a current generating apparatus, and a test apparatus.
More particularly, the present invention relates to a voltage
generating apparatus for outputting a power source voltage, a
current generating apparatus for outputting a power source current,
and a test apparatus for testing a device under test.
[0003] 2. Related Art
[0004] FIG. 7 is a view showing relation of a power source voltage
V.sub.O to a power source current I.sub.O in a voltage generating
apparatus including a conventional current limiting circuit.
Conventionally, there has been known a voltage generating apparatus
including a current limiting circuit that limits an electric
current so that the electric current exceeding a predetermined
value does not flow into a load. The limiting circuit detects a
power source current I.sub.O, and descends a power source voltage
V.sub.O to constant gain when the detected power source current
I.sub.O exceeds a limiting current I.sub.CLP.
[0005] Meanwhile, in a conventional voltage generating apparatus, a
difference between a limiting current I.sub.CLP at the limit start
and a power source current I.sub.SHORT at the load short (a power
source voltage V.sub.O=0) is large. When the power source current
I.sub.SHORT at the load short is large, a conventional voltage
generating apparatus may flow a large current into a load to
destroy the load. Therefore, it is desirable that a difference
between a limiting current I.sub.CLP at the limit start and a power
source current I.sub.SHORT at the load short is small in a voltage
generating apparatus.
SUMMARY OF THE INVENTION
[0006] Therefore, it is an object of the present invention to
provide a voltage generating apparatus, a current generating
apparatus, and a test apparatus that can solve the foregoing
problems. The above and other objects can be achieved by
combinations described in the independent claims. The dependent
claims define further advantageous and exemplary combinations of
the present invention.
[0007] That is, according to the first aspect of the present
invention, there is provided a voltage generating apparatus that
outputs a power source voltage from a voltage outputting terminal.
The voltage generating apparatus includes: a voltage outputting
section that outputs the power source voltage according to a
current or voltage to be input; a first differential amplification
section that compares the power source voltage and a preset first
reference voltage to output a first control current or voltage
reducing the power source voltage output from the voltage
outputting section when the power source voltage is larger than the
first reference voltage and output the first control current or
voltage raising the power source voltage output from the voltage
outputting section when the power source voltage is smaller than
the first reference voltage; a current detector that detects a
detecting voltage according to a power source current output from
the voltage outputting terminal; a second differential
amplification section that compares the detecting voltage detected
from the current detector and a second reference voltage to output
a second control current or voltage reducing the power source
voltage when a value obtained by subtracting the second reference
voltage from the detecting voltage is larger; an addition section
that inputs a current or voltage obtained by adding the first
control current or voltage and the second control current or
voltage into the voltage outputting section; and a third
differential amplification section that supplies a voltage obtained
by amplifying a difference voltage obtained by subtracting the
detecting voltage from a preset third reference voltage to the
second differential amplification section as the second reference
voltage.
[0008] The current detector may include: a series resistor that is
provided on electric wiring between an output of the voltage
outputting section and the voltage outputting terminal; and a
differential amplifier that detects the power source current by
outputting a detecting voltage according to a potential difference
between both ends of the series resistor.
[0009] According to the second aspect of the present invention,
there is provided a current generating apparatus that outputs a
power source current from a current outputting terminal. The
current generating apparatus includes: a current outputting section
that outputs the power source current according to a current or
voltage to be input; a current detector that detects a detecting
voltage according to the power source current output from the
current outputting terminal; a fourth differential amplification
section that compares the detecting voltage and a fourth reference
voltage according to a preset first reference current to output a
first control current or voltage reducing the power source current
output from the current outputting section when the power source
current is larger than the first reference current and output the
first control current or voltage raising the power source current
output from the current outputting section when the power source
current is smaller than the first reference current; a fifth
differential amplification section that compares a power source
voltage at the current outputting terminal and a fifth reference
voltage to output a second control current or voltage reducing the
power source current when a value obtained by subtracting the fifth
reference voltage from the power source voltage is larger; an
addition section that inputs a current or voltage obtained by
adding the first control current or voltage and the second control
current or voltage into the current outputting section; and a sixth
differential amplification section that supplies a voltage obtained
by amplifying a difference voltage obtained by subtracting the
power source voltage from a preset sixth reference voltage to the
fifth differential amplification section as the fifth reference
voltage.
[0010] The current detector may include: a series resistor that is
provided on electric wiring between an output of the current
outputting section and the current outputting terminal; and a
differential amplifier that detects the power source current by
outputting a detecting voltage according to a potential difference
between both ends of the series resistor.
[0011] According to the third aspect of the present invention,
there is provided a test apparatus that tests a device under test.
The test apparatus includes: a voltage generating apparatus that
outputs a power source voltage to be supplied to the device under
test from a voltage outputting terminal; and a test processing
section that tests the device under test in a state that the
voltage generating apparatus has supplied the power source voltage
to the device under test, in which the voltage generating apparatus
includes: a voltage outputting section that outputs the power
source voltage according to a current or voltage to be input; a
first differential amplification section that compares the power
source voltage and a preset first reference voltage to output a
first control current or voltage reducing the power source voltage
output from the voltage outputting section when the power source
voltage is larger than the first reference voltage and output the
first control current or voltage raising the power source voltage
output from the voltage outputting section when the power source
voltage is smaller than the first reference voltage; a current
detector that detects a detecting voltage according to a power
source current output from the voltage outputting terminal; a
second differential amplification section that compares the
detecting voltage detected from the current detector and a second
reference voltage to output a second control current or voltage
reducing the power source voltage when a value obtained by
subtracting the second reference voltage from the detecting voltage
is larger; an addition section that inputs a current or voltage
obtained by adding the first control current or voltage and the
second control current or voltage into the voltage outputting
section; and a third differential amplification section that
supplies a voltage obtained by amplifying a difference voltage
obtained by subtracting the detecting voltage from a preset third
reference voltage to the second differential amplification section
as the second reference voltage.
[0012] According to the fourth aspect of the present invention
there is provided a test apparatus that tests a device under test.
The test apparatus includes: a current generating apparatus that
outputs a power source current to be supplied to the device under
test from a current outputting terminal; and a test processing
section that tests the device under test in a state that the
current generating apparatus has supplied the power source current
to the device under test, in which the current generating apparatus
includes: a current outputting section that outputs the power
source current according to a current or voltage to be input; a
current detector that detects the power source current output from
the current outputting terminal; a fourth differential
amplification section that compares the power source current and a
preset first reference current to output a first control current or
voltage reducing the power source current output from the current
outputting section when the power source current is larger than the
first reference current and output the first control current or
voltage raising the power source current output from the current
outputting section when the power source current is smaller than
the first reference current; a fifth differential amplification
section that compares a power source voltage at the current
outputting terminal and a second reference voltage to output a
second control current or voltage reducing the power source current
when a value obtained by subtracting the second reference voltage
from the power source voltage is larger; an addition section that
inputs a current or voltage obtained by adding the first control
current or voltage and the second control current or voltage into
the current outputting section; and a sixth differential
amplification section that supplies a voltage obtained by
amplifying a difference voltage obtained by subtracting the power
source voltage from a preset third reference voltage to the fifth
differential amplification section as the second reference
voltage.
[0013] The summary of the invention does not necessarily describe
all necessary features of the present invention. The present
invention may also be a sub-combination of the features described
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a view showing a configuration of a test apparatus
according to an embodiment of the present invention along with a
device under test.
[0015] FIG. 2 is a view showing a configuration of a voltage
generating apparatus according to an embodiment of the present
invention along with a device under test.
[0016] FIG. 3 is a view showing relation of a power source voltage
V.sub.O to a power source current I.sub.O in a voltage generating
apparatus according to an embodiment of the present invention.
[0017] FIG. 4 is a view showing a configuration of a current
generating apparatus according to the first alternative example of
the present embodiment along with a device under test.
[0018] FIG. 5 is a view showing relation of a power source current
to a power source voltage V.sub.O in a current generating apparatus
according to the first alternative example.
[0019] FIG. 6 is a view showing a configuration of a voltage
generating apparatus according to the second alternative example of
the present embodiment along with a device under test.
[0020] FIG. 7 is a view showing relation of a power source voltage
V.sub.O to a power source current I.sub.O in a voltage generating
apparatus including a conventional current limiting circuit.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The invention will now be described based on the preferred
embodiments, which do not intend to limit the scope of the present
invention, but exemplify the invention. All of the features and the
combinations thereof described in the embodiment are not
necessarily essential to the invention.
[0022] FIG. 1 is a view showing a configuration of a test apparatus
10 according to an embodiment along with a device under test 100.
The test apparatus 10 includes a voltage generating apparatus 20
and a test processing section 22, and tests the device under test
100. The voltage generating apparatus 20 outputs a power source
voltage V.sub.O to be supplied to the device under test 100 from a
voltage outputting terminal 30 thereof. The test processing section
22 tests the device under test 100 in a state that the voltage
generating apparatus 20 has supplied a power source voltage to the
device under test 100. As an example, the test processing section
22 may have a pattern generating section 24, a test signal
supplying section 26, and a deciding section 28. The pattern
generating section 24 generates a test pattern for designating a
pattern of a test signal. The test signal supplying section 26
supplies a test signal according to a test pattern to the device
under test 100. The deciding section 28 decides the good or bad of
the device under test using an output signal output from the device
under test 100 according to the supplied test signal.
[0023] FIG. 2 is a view showing a configuration of the voltage
generating apparatus 20 according to the present embodiment along
with the device under test 100. The voltage generating apparatus 20
has a voltage outputting section 34, a current detector 36, a first
differential amplification section 38, a second differential
amplification section 40, an addition section 42, and a third
differential amplification section 44. The voltage generating
apparatus 20 outputs the power source voltage V.sub.O to be
supplied to the device under test 100 that is a load from the
voltage outputting terminal 30.
[0024] The voltage outputting section 34 outputs the power source
voltage V.sub.O according to an input current or an input voltage
to be input. The voltage outputting section 34 supplies the power
source voltage V.sub.O to the device under test 100 via the voltage
outputting terminal 30. In the present embodiment, the voltage
outputting section 34 includes a smoothing capacitor 46 and a
voltage outputting circuit 48, and outputs a power source voltage
V.sub.O according to an input current. The smoothing capacitor 46
is charged with electric currents output from the addition section
42 to generate an input voltage V.sub.1 according to an integral
value of electric currents output from the addition section 42
between terminals thereof. The voltage outputting circuit 48
outputs a power source voltage V.sub.O according to the input
voltage V.sub.1 generated between the terminals of the smoothing
capacitor 46.
[0025] The current detector 36 detects a detecting voltage V.sub.X
according to a power source current I.sub.O output from the voltage
outputting terminal 30. In the present embodiment, the current
detector 36 includes a series resistor 50 and a first voltage
output differential amplifier 52. The series resistor 50 is
provided on electric wiring between an output of the voltage
outputting section 34 and the voltage outputting terminal 30, and
generates a voltage difference in proportion to the power source
current I.sub.O on both ends thereof. The first voltage output
differential amplifier 52 outputs a detecting voltage V.sub.X
obtained by amplifying a potential difference between the both ends
of the series resistor 50. The first voltage output differential
amplifier 52 detects the power source current I.sub.O by outputting
the detecting voltage V.sub.X according to the potential difference
between the both ends of the series resistor 50.
[0026] The first differential amplification section 38 compares the
power source voltage V.sub.O and a preset first reference voltage
V.sub.R1. Then, the first differential amplification section 38
outputs a first control current or voltage lowering the power
source voltage V.sub.O output from the voltage outputting section
34 when the power source voltage V.sub.O is larger than the first
reference voltage V.sub.R1, and outputs the first control current
or voltage raising the power source voltage V.sub.O output from the
voltage outputting section 34 when the power source voltage V.sub.O
is smaller than the first reference voltage V.sub.R1. In the
present embodiment, the first differential amplification section 38
includes a first voltage generating section 54 and a first current
output differential amplifier 56. The first voltage generating
section 54 generates the first reference voltage V.sub.R1. The
first current output differential amplifier 56 outputs a first
control current I.sub.1 in proportion to a voltage obtained by
subtracting the power source voltage V.sub.O from the first
reference voltage V.sub.R1 generated from the first voltage
generating section 54.
[0027] The second differential amplification section 40 compares
the detecting voltage V.sub.X according to the power source current
I.sub.O detected from the current detector 36 and a second
reference voltage V.sub.R2 that becomes small as the power source
current I.sub.O becomes larger. Then, the second differential
amplification section 40 outputs a second control current or
voltage lowering the power source voltage V.sub.O when a value
obtained by subtracting the second reference voltage V.sub.R2 from
the detecting voltage V.sub.X according to the power source current
I.sub.O is larger. In the present embodiment, the second
differential amplification section 40 includes a second current
output differential amplifier 58. The second current output
differential amplifier 58 inputs the second reference voltage
V.sub.R2 that becomes small as the power source current I.sub.O
becomes larger and the detecting voltage V.sub.X that becomes large
as the power source current I.sub.O becomes larger. Then, the
second current output differential amplifier 58 outputs a second
control current I.sub.2 in proportion to a voltage obtained by
subtracting the detecting voltage V.sub.X from the second reference
voltage V.sub.R2. Furthermore, the second current output
differential amplifier 58 sets the second control current I.sub.2
to zero when the detecting voltage V.sub.X shows that the power
source current I.sub.O is less than a limiting current
I.sub.CLP.
[0028] The addition section 42 supplies a current or voltage
obtained by adding the first control current or voltage output from
the first differential amplification section 38 and the second
control current or voltage output from the second differential
amplification section 40 to the voltage outputting section 34 as an
input current or an input voltage V.sub.1. In the present
embodiment, the addition section 42 includes a current adder 60.
The current adder 60 outputs an electric current obtained by adding
the first control current I.sub.1 output from the first current
output differential amplifier 56 and the second control current
I.sub.2 output from the second current output differential
amplifier 58. As an example, the current adder 60 may be a
connecting point for connecting an output port of the first current
output differential amplifier 56, an output port of the second
current output differential amplifier 58, and an input port of the
voltage outputting section 34. In this way, the current adder 60
can charge the smoothing capacitor 46 with electric currents
obtained by adding the first control current I.sub.1 and the second
control current I.sub.2. Therefore, the current adder 60 can input
the input voltage V.sub.1 according to an integral value of the
electric currents into the voltage outputting circuit 48.
[0029] The third differential amplification section 44 supplies a
voltage obtained by amplifying a difference voltage obtained by
subtracting the detecting voltage V.sub.X according to the power
source current I.sub.O from a preset third reference voltage
V.sub.R3 to the second differential amplification section 40 as the
second reference voltage V.sub.R2. In this way, the third
differential amplification section 44 can output the second
reference voltage V.sub.R2 that becomes small as the power source
current to becomes larger.
[0030] In the present embodiment, the third differential
amplification section 44 includes a second voltage generating
section 62, a first resistor 64, a second resistor 66, and a second
voltage output differential amplifier 68. The second voltage
generating section 62 generates the third reference voltage
V.sub.R3. The first resistor 64 and the second resistor 66 subtract
the third reference voltage V.sub.R3 generated from the second
voltage generating section 62 from the detecting voltage V.sub.X
output from the first voltage output differential amplifier 52, in
order to generate a partial-pressure voltage ((V.sub.X-V.sub.R3)/2)
obtained by dividing the subtracted result by a predetermined
resistance ratio (for example, 1/2). The second voltage output
differential amplifier 68 supplies the second reference voltage
V.sub.R2 in proportion to a voltage obtained by subtracting the
partial-pressure voltage ((V.sub.X-V.sub.R3)/2) generated by the
first resistor 64 and the second resistor 66 from a ground voltage
(0V) to the second current output differential amplifier 58. In
this way, the second voltage output differential amplifier 68 can
output the second reference voltage V.sub.R2 that becomes small as
the power source current I.sub.O becomes larger.
[0031] FIG. 3 is a view showing relation of the power source
voltage V.sub.O to the power source current I.sub.O in the voltage
generating apparatus 20 according to the present embodiment. In
addition, a thick dotted line in FIG. 3 shows the power source
voltage V.sub.O to the power source current to when it is assumed
that there is not the third differential amplification section
44.
[0032] The first current output differential amplifier 56 increases
or decreases the first control current I.sub.1 to be output so as
to control the power source voltage V.sub.O to a predetermined
value. When the power source current I.sub.O is less than or equal
to the limiting current I.sub.CLP, the second current output
differential amplifier 58 sets the second control current I.sub.2
to zero. In this way, according to the voltage generating apparatus
20, when the power source current I.sub.O is less than or equal to
the limiting current I.sub.CLP, it is possible to stably output a
predetermined power source voltage V.sub.O by the control by the
first current output differential amplifier 56.
[0033] Then, when the power source current I.sub.O exceeds the
limiting current I.sub.CLP, the second current output differential
amplifier 58 supplies the minus second control current I.sub.2, an
absolute value of which becomes large as the power source current
I.sub.O becomes large, to the current adder 60. In other words, the
second current output differential amplifier 58 absorbs an amount
of the current that becomes large as the power source current
I.sub.O becomes large from the current adder 60. As a result, the
second current output differential amplifier 58 absorbs, from the
current adder 60, an electric current for an amount of the first
control current I.sub.1 output from the first current output
differential amplifier 56, and additionally absorbs electric
charges charged in the smoothing capacitor 46. Therefore, the
second current output differential amplifier 58 reduces the input
voltage V.sub.1 for the voltage outputting circuit 48.
[0034] In this way, the voltage generating apparatus 20 can reduce
the power source voltage V.sub.O when the power source current
I.sub.O exceeds the limiting current I.sub.CLP, in order to control
an excess current not to flow into the device under test 100.
[0035] Furthermore, the second current output differential
amplifier 58 outputs the second control current I.sub.2 with an
amount of the current according to the difference between the
second reference voltage V.sub.R2 that becomes small as the power
source current I.sub.O becomes larger by the control of the third
differential amplification section 44 and the detecting voltage
V.sub.X according to the power source current I.sub.O. In this way,
as shown with a solid line in FIG. 3, the voltage generating
apparatus 20 can reduce the power source voltage V.sub.O as the
power source current I.sub.O becomes large with higher DC precision
in a range in which the power source current I.sub.O exceeds the
limiting current I.sub.CLP. Therefore, the voltage generating
apparatus 20 can reduce the difference between the limiting current
I.sub.CLP at the limit start and a power source current I.sub.SHORT
at short of the voltage outputting terminal 30, in order to limit
the power source current I.sub.O with a good characteristic.
[0036] In addition, as an example, the third differential
amplification section 44 for outputting the second reference
voltage V.sub.R2 reduces an amplification degree in a
high-frequency area (for example, an amplification degree is one),
and increases an amplification degree in a low-frequency area (for
example, A.sub.2 (A.sub.2 is a value higher than one)). In other
words, the third differential amplification section 44 may reduce
an amplification degree in frequency higher than fluctuation
frequency of the power source current I.sub.O according to the
fluctuation of a load (for example, one), and increases an
amplification degree in frequency less than or equal to fluctuation
frequency of the power source current I.sub.O according to the
fluctuation of a load (for example, A.sub.2). In this way, since
the voltage generating apparatus 20 can reduce loop gain to limit
the power source current I.sub.O in a high-frequency area, it is
possible to stably reduce the power source current I.sub.O.
[0037] FIG. 4 is a view showing a configuration of a current
generating apparatus 70 according to the first alternative example
of the present embodiment along with the device under test 100. In
addition, since the current generating apparatus 70 shown in FIG. 4
has the generally same configuration and function as those of the
voltage generating apparatus 20 shown in FIG. 2, their descriptions
will be omitted except points of difference about the generally
same components as those included in the voltage generating
apparatus 20.
[0038] The test apparatus 10 may include the current generating
apparatus 70 that outputs a power source current I.sub.O to be
supplied to the device under test 100 from a current outputting
terminal 80, in place of the voltage generating apparatus 20. The
current generating apparatus 70 has a current detector 36, an
addition section 42, a current outputting section 82, a fourth
differential amplification section 84, a fifth differential
amplification section 86, and a sixth differential amplification
section 88. The current detector 36 detects the power source
current I.sub.O output from the current outputting terminal 80. In
the present alternative example, the current detector 36 includes a
series resistor 50 and a first voltage output differential
amplifier 52. The series resistor 50 is provided on electric wiring
between the current outputting section 82 and the current
outputting terminal 80.
[0039] The current outputting section 82 outputs the power source
current I.sub.O according to an input current or input voltage to
be input. The current outputting section 82 supplies the power
source current to the device under test 100 via the current
outputting terminal 80. In the present alternative example) the
current outputting section 82 includes a smoothing capacitor 46 and
a current outputting circuit 90. The current outputting circuit 90
outputs the power source current I.sub.O according to an input
voltage V.sub.1 generated on the smoothing capacitor 46.
[0040] The fourth differential amplification section 84 compares a
detecting voltage V.sub.X according to the power source current
I.sub.O and a preset fourth reference voltage V.sub.R4, Then, the
fourth differential amplification section 84 outputs a first
control current or voltage reducing the power source current
I.sub.O output from the current outputting section 82 when the
power source current I.sub.O is larger than the fourth reference
voltage V.sub.R4, and outputs the first control current or voltage
raising the power source current I.sub.O output from the current
outputting section 82 when the power source current I.sub.O is
smaller than the fourth reference voltage V.sub.R4. In the present
alternative example, the fourth differential amplification section
84 includes a first voltage generating section 54 and a first
current output differential amplifier 56. The first current output
differential amplifier 56 outputs a first control current I.sub.1
in proportion to a voltage obtained by subtracting a detecting
voltage V.sub.X detected from the current detector 36 from the
fourth reference voltage V.sub.R4 generated from the first voltage
generating section 54.
[0041] The fifth differential amplification section 86 compares the
power source voltage V.sub.O of the current outputting terminal 80
and a fifth reference voltage V.sub.R5 that becomes small as the
power source voltage V.sub.O becomes larger. Then, the fifth
differential amplification section 86 outputs a second control
current or voltage preferably reducing the power source current
I.sub.O when a value obtained by subtracting the fifth reference
voltage V.sub.R5 from the power source voltage V.sub.O is larger.
In the present alternative example, the fifth differential
amplification section 86 includes a second current output
differential amplifier 58. The second current output differential
amplifier 58 inputs the fifth reference voltage V.sub.R5 and the
power source voltage V.sub.O. Then, the second current output
differential amplifier 58 outputs a second control current I.sub.2
in proportion to a voltage obtained by subtracting the power source
voltage V.sub.O from the fifth reference voltage V.sub.R5.
Furthermore, the second current output differential amplifier 58
sets the second control current I.sub.2 to zero when the power
source voltage V.sub.O is less than or equal to a limiting voltage
V.sub.CLP.
[0042] The sixth differential amplification section 88 supplies a
voltage obtained by amplifying a difference voltage obtained by
subtracting the power source voltage V.sub.O from a preset sixth
reference voltage V.sub.R6 to the fifth differential amplification
section 86 as the fifth reference voltage V.sub.R5. In this way,
the sixth differential amplification section 88 can supply the
fifth reference voltage V.sub.R5 that becomes small as the power
source voltage V.sub.O becomes larger.
[0043] In the present alternative example, the sixth differential
amplification section 88 includes a second voltage generating
section 62, a first resistor 64, a second resistor 66, and a second
voltage output differential amplifier 68. The first resistor 64 and
the second resistor 66 subtract the sixth reference voltage
V.sub.R6 generated from the second voltage generating section 62
from the output voltage V.sub.O, in order to generate a
partial-pressure voltage ((V.sub.O-V.sub.R3)/2) obtained by
dividing the subtracted result by a predetermined resistance ratio
(for example, 1/2). The second voltage output differential
amplifier 68 supplies the fifth reference voltage V.sub.R5 in
proportion to a voltage obtained by subtracting the
partial-pressure voltage ((V.sub.O-V.sub.R3)/2) generated by the
first resistor 64 and the second resistor 66 from a ground voltage
(0V) to the second current output differential amplifier 58. In
this way, the second voltage output differential amplifier 68 can
supply the fifth reference voltage VR.sub.5 that becomes small as
the power source voltage V.sub.O becomes larger, to the second
current output differential amplifier 58.
[0044] FIG. 5 is a view showing relation of a power source current
I.sub.O to a power source voltage V.sub.O in the current generating
apparatus 70 according to the present embodiment. In addition, a
thick dotted line in FIG. 5 shows the power source current I.sub.O
the power source voltage V.sub.O when it is assumed that there is
not the sixth differential amplification section 88.
[0045] The first current output differential amplifier 56 increases
or decreases the first control current I.sub.1 to be output so as
to control the power source current I.sub.O to a predetermined
value. When the power source voltage V.sub.O is less than or equal
to the limiting voltage V.sub.CLP, the second current output
differential amplifier 58 sets the second control current I.sub.2
to zero. In this way, according to the current generating apparatus
70, when the power source voltage V.sub.O is less than or equal to
the limiting voltage V.sub.CLP, it is possible to stably output a
predetermined power source current I.sub.O by the control by the
first current output differential amplifier 56.
[0046] Then, when the power source voltage V.sub.O exceeds the
limiting voltage V.sub.CLP, the second current output differential
amplifier 58 supplies the minus second control current I.sub.2, an
absolute value of which becomes large as the power source voltage
V.sub.O becomes large, to the current adder 60. In other words, the
second current output differential amplifier 58 absorbs an amount
of the current that becomes large as the power source voltage
V.sub.O becomes large from the current adder 60. As a result the
second current output differential amplifier 58 absorbs, from the
current adder 60, an electric current for an amount of the first
control current I.sub.1 output from the first current output
differential amplifier 56, and additionally absorbs electric
charges charged in the smoothing capacitor 46. Therefore, the
second current output differential amplifier 58 reduces the input
voltage V.sub.1 for the current outputting circuit 82.
[0047] In this way, the current generating apparatus 70 can reduce
the power source current I.sub.O when the power source voltage
V.sub.O exceeds the limiting voltage V.sub.CLP, in order to control
an excess voltage not to flow into the device under test 100.
[0048] Furthermore, the second current output differential
amplifier 58 outputs the second control current I.sub.2 with an
amount of the current according to the difference between the fifth
reference voltage V.sub.R5 that becomes small as the power source
voltage V.sub.O0 becomes larger by the control of the sixth
differential amplification section 88 and the detecting voltage
V.sub.X according to the power source voltage V.sub.O. In this way,
as shown with a solid line in FIG. 5, the current generating
apparatus 70 can reduce the power source current I.sub.O as the
power source voltage V.sub.O becomes large with higher DC precision
in a range in which the power source voltage V.sub.O exceeds the
limiting voltage V.sub.CLP. Therefore, the current generating
apparatus 70 can reduce the difference between the limiting voltage
V.sub.CLP at the limit start and a power source voltage V.sub.OPEN
at open of the voltage outputting terminal 30, in order to limit
the power source voltage V.sub.O with a good characteristic.
[0049] In addition, as an example, the sixth differential
amplification section 88 for outputting the fifth reference voltage
V.sub.R5 reduces an amplification degree in a high-frequency area
(for example, an amplification degree is one), and increases an
amplification degree in a low-frequency area (for example, A.sub.2
(A.sub.2 is a value higher than one)). In other words, the sixth
differential amplification section 88 may reduce an amplification
degree in frequency higher than fluctuation frequency of the power
source voltage V.sub.O according to the fluctuation of a load (for
example, one), and increases an amplification degree in frequency
less than or equal to fluctuation frequency of the power source
voltage V.sub.O according to the fluctuation of a toad (for
example, A.sub.2). In this way, since the current generating
apparatus 70 can reduce loop gain to limit the power source voltage
V.sub.O in a high-frequency area, it is possible to stably reduce
the power source voltage V.sub.O.
[0050] FIG. 6 is a view showing a configuration of a voltage
generating apparatus 20 according to the second alternative example
of the present embodiment along with the device under test 100. In
addition, since the voltage generating apparatus 20 shown in FIG. 6
has the generally same configuration and function as those of the
voltage generating apparatus 20 shown in FIG. 2, their descriptions
will be omitted except points of difference about the generally
same components as those included in the voltage generating
apparatus 20 shown in FIG. 2.
[0051] A second differential amplification section 40 according to
the present alternative example has a third current output
differential amplifier 110, a fourth current output differential
amplifier 112, and a seventh differential amplification section
114.
[0052] The third current output differential amplifier 110 inputs a
second reference voltage V.sub.R2 that becomes small as a power
source current I.sub.O becomes larger and a detecting voltage
V.sub.X that becomes large as the power source current I.sub.O
becomes larger. Then, the third current output differential
amplifier 110 outputs a plus current I.sub.2-1 in proportion to a
voltage obtained by subtracting the detecting voltage V.sub.X from
the second reference voltage V.sub.R2. Furthermore, the third
current output differential amplifier 110 sets the current
I.sub.2-1 to zero when the detecting voltage V.sub.X shows that the
power source current I.sub.O is not less than a limiting current
I.sub.CLP.
[0053] The fourth current output differential amplifier 112 inputs
a seventh reference voltage V.sub.R7 that becomes small as the
power source current I.sub.O becomes larger and the detecting
voltage V.sub.X that becomes large as the power source current
I.sub.O becomes larger. Then, the fourth current output
differential amplifier 112 outputs a minus current I.sub.2-2 of
which the size of an absolute value is proportional to a voltage
obtained by subtracting the seventh reference voltage V.sub.R7 from
the detecting voltage V.sub.X. In other words, the fourth current
output differential amplifier 112 absorbs the current I.sub.2-2. In
this case, as an example, the fourth current output differential
amplifier 112 may have mutual conductance of which polarity is
opposite to the third current output differential amplifier 110 and
an absolute value is the generally same as each other. Furthermore,
the fourth current output differential amplifier 112 sets the
current I.sub.2-2 to zero when the detecting voltage V.sub.X shows
that the power source current I.sub.O is not more than an inverse
limiting current -I.sub.CLP.
[0054] The seventh differential amplification section 114 supplies
a voltage obtained by amplifying a difference voltage obtained by
subtracting the detecting voltage V.sub.X according to the power
source current I.sub.O from a preset eighth reference voltage
V.sub.R8 to the fourth current output differential amplifier 112 as
the seventh reference voltage VR.sub.7. In this way, the seventh
differential amplification section 114 can output the seventh
reference voltage V.sub.R7 that becomes small as the power source
current I.sub.O becomes larger.
[0055] In the present example, as an example, the seventh
differential amplification section 114 may include a third voltage
generating section 122, a third resistor 124, a fourth resistor
126, and a third voltage output differential amplifier 128. The
third voltage generating section 122 generates an eighth reference
voltage V.sub.R8, The third resistor 124 and the fourth resistor
126 subtract the eighth reference voltage V.sub.R8 generated from
the third voltage generating section 122 from the detecting voltage
V.sub.X output from the first voltage output differential amplifier
52, in order to generate a partial-pressure voltage
((V.sub.X-VR.sub.8)/2) obtained by dividing the subtracted result
by a predetermined resistance ratio (for example, 1/2). The third
voltage output differential amplifier 128 supplies the seventh
reference voltage V.sub.R7 in proportion to a voltage obtained by
subtracting the partial-pressure voltage ((V.sub.X-V.sub.R8)/2)
generated from the third resistor 124 and the fourth resistor 126
from a ground voltage (0V) to the fourth current output
differential amplifier 112. As an example, the third voltage output
differential amplifier 128 may have an amplification factor
generally same as that of the second voltage output differential
amplifier 68 included in the third differential amplification
section 44. In this way, the third voltage output differential
amplifier 128 can output the seventh reference voltage V.sub.R7
that becomes small as the power source current I.sub.O becomes
larger.
[0056] According to the second differential amplification section
40 as described above, since the current I.sub.2-1 output from the
third current output differential amplifier 110 and the current
I.sub.2-2 absorbed by the fourth current output differential
amplifier 112 are generally identical with each other when the
power source current I.sub.O is larger than the inverse limiting
current -I.sub.CLP and smaller than the limiting current I.sub.CLP,
it is possible to set the second control current I.sub.2 to
zero.
[0057] Then, according to the second differential amplification
section 40, since the current I.sub.2-1 output from the third
current output differential amplifier 110 becomes zero and the
current I.sub.2-2 absorbed by the fourth current output
differential amplifier 112 is not changed when the power source
current I.sub.O is not less than the limiting current I.sub.CLP, it
is possible to absorb the current I.sub.2 (-I.sub.2-2) from the
addition section 42.
[0058] Furthermore, according to the second differential
amplification section 40, since the current I.sub.2-2 absorbed by
the fourth current output differential amplifier 112 becomes zero
and the current I.sub.2-1 output from the third current output
differential amplifier 110 is not changed when the power source
current I.sub.O is not more than the inverse limiting current
-I.sub.CLP, it is possible to supply the current I.sub.2
(=I.sub.2-1) to the addition section 42.
[0059] As described above, according to the voltage generating
apparatus 20 of the present alternative example, it is possible to
limit a plus or minus power source current I.sub.O. In addition, a
configuration of the second differential amplification section 40
according to the present example can be applied to the fifth
differential amplification section 86 shown in FIG. 5 by inputting
a power source voltage V.sub.O in place of a detecting voltage
V.sub.X.
[0060] Although the present invention has been described by way of
an exemplary embodiment, it should be understood that those skilled
in the art might make many changes and substitutions without
departing from the spirit and the scope of the present invention.
It is obvious from the definition of the appended claims that
embodiments with such modifications also belong to the scope of the
present invention.
[0061] As apparent from the above descriptions, according to the
present invention, it is possible to realize a voltage generating
apparatus, a current generating apparatus, and a test apparatus for
limiting a power source current and a power source voltage with a
good characteristic.
* * * * *