JP2002286815A - D.c. characteristic testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a d.c. characteristic testing device that is high in measuring accuracy in VSIM mode and can correspond to both DC tests. SOLUTION: In VSIM mode, switches S1 and S2 are turned on and switches S3 and S4 are turned off. Selected first differential amplifier controls a set voltage 101 and a testing voltage 102 so that they may be equivalent to each other. A first current mirror circuit 5 supplies a reference current I5a and an output current I5b respectively. A second current mirror circuit 6 returns a reference current I6a and an output current I6b respectively. A complementary emitter follower circuit 7 supplies a differential current ΔIa, a difference between the reference current I5a and reference current I6a, to a DUT. An ammeter 8 measures a differential current ΔIb, a difference between the output current I5b and output current I6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for testing DC characteristics, and more particularly to an apparatus for testing DC characteristics of a semiconductor integrated circuit (hereinafter referred to as DC test).

[0002]

2. Description of the Related Art A manufactured integrated circuit is examined by a product test to determine whether it meets specifications as designed. The product test includes a function test in which an input signal is supplied, an output signal is observed and compared with an expected value, an AC test in which an AC characteristic such as a delay time, an access time, and a setup / hold time is examined, or an input / output current, an input / A DC test for checking DC characteristics such as an output voltage is used.

[0003] The DC characteristic test apparatus performs a DC test on an integrated circuit which is a circuit under test (hereinafter, referred to as a DUT). For DC test, a constant voltage applied current measurement (V Source I Measu
re: VSIM) and constant current applied voltage measurement (I Source V Measure) for measuring a voltage by supplying a constant current to the DUT
re: ISVM). Various types of DC characteristic test devices that can handle the DC test are manufactured. (For example, see JP-A-6-258382)
No.)

FIG. 4 is a block diagram of an IC test apparatus (DC characteristic test apparatus) described in Japanese Patent Application Laid-Open No. 7-244125. This DC characteristic test apparatus omits the circuit part related to the function test function, and shows only the circuit part related to the DC test function.

The control section 44 inputs a control signal 141 to the variable current source 51, inputs a control signal 142 to the variable current source 52 of the differential circuit 47, and sends a set voltage 143 to the base of the transistor 63 of the differential circuit 46. To enter. Variable current source 51
Supplies a constant current Isc from the positive power supply to the measurement terminal 71 based on the control signal 141.

A current source 61 supplies a predetermined constant current from the emitters of transistors 62 and 63 configured as ECL to a negative power supply. The constant current of the current source 61 is the current Isc or I
This is a sufficiently small value compared to sk. The differential circuit 46 is
The voltage of the measuring terminal 71 and the set voltage 143 input to the bases of the transistors 62 and 63, respectively, are compared, and one of the two collector voltages rises and the other falls according to the comparison result.

The bases of the transistors 53 and 54 receive the collector voltages of the transistors 63 and 62, respectively. The current Ic1 flows from the measurement terminal 71 to the collector of the transistor 53, and the collector of the transistor 54
The current Ic2 flows from the current measuring unit 45. Variable current source 52
Calculates a constant current Isk based on the control signal 142
The current flows from the emitters of the transistors 53 and 54 configured as L to the negative power supply.

In the differential circuit 47, one of the currents Ic1 and Ic2 increases and the other decreases by changing the base voltages of the transistors 53 and 54 based on the comparison result of the differential circuit 46. The relationship between the currents Ic1, Ic2, and Isk is shown as follows. Isk = Ic1 + Ic2 (1)

In the case of the VSIM mode, the control unit 44
The UT 41 sets a set voltage 143 substantially equal to the voltage input to the measurement terminal 71. If the voltage of the measurement terminal 71 is higher than the set voltage 143, Ic1> Ic2, and the voltage of the measurement terminal 71 is decreased.
If it is lower, Ic1 <Ic2, and the potential of the measurement terminal 71 is increased.

By the above operation, the potential of the measuring terminal 71 becomes equal to the set voltage 143, and the current flowing into and out of the measuring terminal becomes zero. The current Idut is shown as follows. Idut = Ic1−Isc (2)

Equation (3) is derived from equations (1) and (2). Idut = Isk-Ic2-Isc (3) The currents Isk and Isc are known. The current measuring unit 45
The current Ic2 is measured. The DC characteristic tester has a measuring terminal 7
The current Idut can be measured under the condition that the voltage of 1 is constant.

In the case of the ISVM mode, the control unit 44
The set voltage 143 is set sufficiently lower than the voltage input to the measurement terminal 71 by the UT 41. When the transistor 53 is turned on and the transistor 54 is turned off, Ic2 = 0.
Therefore, the current Idut is expressed as follows from Expression (3). Idut = Isk-Isc (4)

The voltage measuring unit 43 measures the voltage of the measuring terminal 71 input via the buffer
Measured as The DC characteristic tester can measure the voltage of the measurement terminal 71 under the condition that the current Idut is constant.

[0014]

In the above-described conventional DC characteristic test apparatus, the control unit 44 controls the set voltage 143 so as to cope with the DC test in both the VSIM mode and the ISVM mode. Current I at VSIM
dut is connected to the DUT 4 from the positive power supply via the variable current source 51.
1 or from the DUT 41 to the negative power supply via the variable current source 52.

In the DC characteristics test apparatus, although the output impedance viewed from the measurement terminal 71 is desirably 0Ω, the output impedance is high because the current Idut flows through the variable current source 51 or 52. That is,
According to this conventional technique, even if a circuit is configured as a negative feedback circuit, the output impedance is about several hundred Ω to several kΩ, so that a voltage drop corresponding to the product of the current Idut and the output impedance occurs, and the measured voltage 144 An error occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and VS
It is an object of the present invention to provide a DC characteristic test apparatus which has high measurement accuracy in the IM mode and can cope with both DC tests.

[0017]

In order to achieve the above object, a DC characteristics test apparatus according to the present invention supplies a constant voltage to a circuit to be tested connected to a test terminal and measures a current. In a DC characteristic test apparatus that operates in one of a VSIM mode and an ISVM mode in which a constant current is supplied to measure a voltage, a voltage source that generates a set voltage corresponding to the fixed voltage; A first differential amplifier connected to a non-inverting terminal, wherein the test terminal is connected to an inverting terminal; and the test terminal is connected to a non-inverting terminal,
A second differential amplifier having an output terminal fed back to an inverting terminal, a switching circuit for selecting the first differential amplifier in the VSIM mode, and selecting the second differential amplifier in the ISVM mode; A current supply circuit that supplies a first reference current from a first power supply voltage, a current circulation circuit that circulates a second reference current from a second power supply voltage, and a pair of emitter followers; A complementary emitter follower circuit for circulating a first reference current and supplying the second reference current from the other collector, a first current source for supplying a first set current, and a second set current. The second to reflux
And measuring the output current from the circuit under test in the VSIM mode by measuring the difference between the first reference current and the second reference current that are generated by the current. In the ISVM mode, the constant current is supplied to the test target circuit by a difference between the first set current and the second set current,
The output voltage of the circuit under test is measured by measuring the output voltage of the second differential amplifier.

According to the DC characteristics test apparatus of the present invention, a low output impedance can be realized in the VSIM mode, and the test voltage can be set accurately. Therefore, the measurement accuracy is improved, and the switching circuit is provided with the first or second differential circuit. The dynamic amplifier is selected, so the DC in both VSIM mode and ISVM mode
Can respond to tests.

In the DC characteristic test apparatus of the present invention, the VS
In the IM mode, it is preferable that the first differential amplifier operates so that the non-inverting terminal and the inverting terminal have the same potential. In this case, since the first differential amplifier operates as a negative feedback circuit, the output impedance in the VSIM mode can be reduced, and the test voltage can be set accurately.

In the DC characteristics test apparatus of the present invention, the current supply circuit and the current return circuit may include a pair of reference current lines connected to the test terminals and output current lines connected to each other. It is preferable that an ammeter is connected between the output side current line and the ground. In this case, the direct connection between the complementary emitter follower circuit and the circuit to be tested can reduce the resistance of the ammeter or the like, so that the output impedance in the VSIM mode is further reduced.

It is also a preferred embodiment of the present invention that a voltmeter is connected between the output terminal of the second differential amplifier and the ground. In this case, since the second differential amplifier operates as a voltage follower and does not affect the constant current supplied to the circuit under test, the measurement in the ISVM mode becomes accurate.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a direct current characteristic testing apparatus according to the present invention. FIG. 1 shows a VSIM mode of a DC characteristic test apparatus according to an embodiment of the present invention.

The DC characteristics test apparatus includes a differential input stage switching amplifier circuit 1, a voltage source 2, a first emitter follower circuit 3, a second emitter follower circuit 4, a first current mirror circuit 5, a second current mirror circuit 6, It comprises a complementary emitter follower circuit 7, an ammeter 8, diodes 9, 10, a second current source 11, a first current source 12, a voltmeter 13, and current cutoff switches S3 and S4. A DUT is connected to the test terminal 14 of the DC characteristics test device.

The first emitter follower circuit 3 comprises an NPN transistor Qn1, an ON / OFF switch S1, and a constant current source 21. Second emitter follower circuit 4
Is a PNP transistor Qp1, an ON-OFF switch S
2 and a constant current source 22. The complementary emitter follower circuit 7 includes an NPN transistor Qn2 and a PNP
It is composed of a transistor Qp2.

The DC characteristics test apparatus has a control unit (not shown). The control unit generates a selection signal according to the test mode to be selected, and switches the switch S5 of the differential input stage switching amplifier circuit 1 and the ON-OF of the first emitter follower circuit 3.
F-switch S1, ON of second emitter follower circuit 4
It is input to the control terminals of the OFF switch S2, the current cutoff switch S3, and the current cutoff switch S4. The control unit generates a setting signal according to the measurement, and outputs a voltage source 2 and a second current source 1
1 and input to the first current source 12.

The differential input stage switching amplifier circuit 1 comprises a first differential amplifier comprising a non-inverting terminal 31 and an inverting terminal 32, a second differential amplifier comprising a non-inverting terminal 33 and an inverting terminal 34,
And a changeover switch S5.

The differential input stage switching amplifier circuit 1 is supplied with positive power and negative power. The set voltage 101 is supplied to the non-inverting terminal 31 by the voltage source 2. Inverting terminal 32
And the non-inverting terminal 33 are commonly connected and connected to the test terminal 14. The test terminal 14 is connected to the anode of the diode 9, the cathode of the diode 10, and the emitters of the transistors Qn2 and Qp2. The output terminal 35 of the differential input stage switching amplifier circuit 1 is connected to transistors Qn1 and Qn.
The voltmeter 1 is connected to the base of p1 and the inverting terminal 34.
3 is connected to the ground.

The collector of the transistor Qn1 of the first emitter follower circuit 3 is connected to a positive power supply. The emitter of the transistor Qn1 is connected to the anode of the diode 10 and the base of the transistor Qp2, connected to the negative power supply via the switch S1 and the constant current source 21, and connected to the switch S4.
And a positive power supply via the first current source 12.

The collector of the transistor Qp1 of the second emitter follower circuit 4 is connected to a negative power supply. The emitter of the transistor Qp1 is connected to the cathode of the diode 9 and the base of the transistor Qn2, to the positive power supply via the switch S2 and the constant current source 22, and to the negative power supply via the switch S3 and the second current source 11. Is done.

The first current mirror circuit 5 is supplied with positive power, and the second current mirror circuit 6 is supplied with negative power. The reference current terminal of the first current mirror circuit 5 is connected to the collector of the transistor Qn2.
The current terminal on the output side of the first current mirror circuit 5
Connected to the current terminal on the output side of the current mirror circuit 6,
It is connected to ground via an ammeter 8. The reference current terminal of the second current mirror circuit 6 is connected to the collector of the transistor Qp2.

FIG. 2 shows a specific example of the differential input stage switching amplifier circuit 1 of FIG. The differential input stage switching amplifier circuit 1 includes an output circuit 23, an input stage of a first differential amplifier including NPN transistors Qn3 and Qn4, an input stage of a second differential amplifier including NPN transistors Qn5 and Qn6, and an NPN transistor. It has a changeover switch S5 consisting of Qn7 and Qn8. The output circuit 23 is a circuit that realizes a function required as an operational amplifier with functions other than the input stage of the first differential amplifier, the input stage of the second differential amplifier, and the changeover switch S5.

The changeover switch S5 selects one of the first differential amplifier and the second differential amplifier based on a selection signal from the control unit. Differential input stage switching amplifier circuit 1
Operates with a circuit function configured by the selected differential amplifier, generates an output voltage based on a signal between the non-inverting terminal and the inverting terminal, and inputs the output voltage to the output terminal 35. The first differential amplifier forms a negative feedback circuit, and the second differential amplifier forms a voltage follower circuit.

The voltage source 2 generates a set voltage 101 corresponding to a constant voltage in the VSIM mode based on a set signal from the control unit. In the constant current sources 21 and 22, the switches S1 and S2 are turned on and the transistors Qp2 and Qn2 are turned on based on the setting signal.

The first current mirror circuit 5 supplies a reference current I5a (first reference current) from a current terminal on the reference side, and supplies an output current I5b having the same value as the reference current I5a from a current terminal on the output side. .
The second current mirror circuit 6 circulates a reference current I6a (second reference current) from the reference-side current terminal, and circulates an output current I6b having the same value as the reference current I6a from the output-side current terminal.

In the VSIM mode, the control unit controls the VSIM
A mode selection signal and a setting signal are generated. ON-OF
The F switches S1 and S2 are turned on. Transistor Qn
1, Qp1, Qn2 and Qp2 are turned on. First
The emitter follower circuit 3, the second emitter follower circuit 4, and the complementary emitter follower circuit 7 start operating.

The changeover switch S5 selects the first differential amplifier. In the differential input stage switching amplifier circuit 1, the selected first differential amplifier operates as a negative feedback circuit, and the set voltage 1
01 and the test voltage 102 generated at the test terminal 14 are controlled. DUT connected to test terminal 14
Is supplied with a test voltage 102 equal to the set voltage 101.

The current cutoff switches S3 and S4 are turned off. The first current source 12 and the second current source 11 stop operating.

The first current mirror circuit 5 supplies a reference current I5a from the reference-side current terminal to the collector of the transistor Qn2 of the complementary emitter follower circuit 7, and outputs the output current to the ammeter 8 from the output-side current terminal. I
Supply 5b.

The second current mirror circuit 6 supplies the reference current I6a from the collector of the transistor Qp2 of the complementary emitter follower circuit 7 to the current terminal on the reference side.
And the output current I6b is returned from the ammeter 8 to the current terminal on the output side.

A difference occurs between the reference current I5a and the reference current I6a by a value equal to the current ΔIa flowing to the DUT via the test terminal 14. The ammeter 8 circulates a difference current ΔIb, which is a difference between the output current I5b and the output current I6b.

The currents ΔIa and ΔIb are represented as follows. ΔIa = I5a−I6a (5) ΔIb = I5b−I6b (6) Since there is a relationship of I5a = I5b and I6a = I6b, ΔIa = ΔIb (7)

As shown in equation (7), by measuring the difference current ΔIb flowing through the ammeter 8, the current ΔIa flowing through the DUT can be measured indirectly.

In the differential input stage switching amplifier circuit 1, the selected first differential amplifier operates as a negative feedback circuit. In this case, a low output impedance state is realized by the operation of the emitter follower circuit and the negative feedback circuit, and the test voltage 1
02 can be exactly equal to the set voltage 101, so that VS
The measurement accuracy in the IM mode is increased.

FIG. 3 shows the ISV of the DC characteristic test apparatus shown in FIG.
Shows the M mode. In the ISVM mode, the control unit controls the IS
A VM mode selection signal and a setting signal are generated. ON-
The OFF switches S1 and S2 are turned off. Transistor Q
n1, Qp1, Qn2, and Qp2 are turned off. First
The emitter follower circuit 3 and the second emitter follower circuit 4 stop operating.

The changeover switch S5 selects the second differential amplifier. In the differential input stage switching amplifier circuit 1, the selected second differential amplifier operates as a voltage follower circuit, and generates an output voltage 103 equal to the test voltage 102;
Input to voltmeter 13. If the voltage of the voltmeter 13 is measured, the voltage supplied to the DUT can be measured.

The current cutoff switches S3 and S4 are turned on. The first current source 12 and the second current source 11 start operating. The first current source 12 supplies a set current 105 to the diode 10 via the current cutoff switch S4.
The second current source 11 circulates the set current 104 from the diode 9 via the current cutoff switch S3.

The diodes 9 and 10 are forward-biased to make the base-emitter voltages of the transistors Qn2 and Qp2 0 V or reverse bias. Transistor Qn2
And Qp2 are turned off. The complementary emitter follower circuit 7, the first current mirror circuit 5, and the second current mirror circuit 6 stop operating.

The diodes 9 and 10 supply the difference current ΔIc to the DUT via the test terminal 14. Difference current ΔI
c is the difference between the set current 105 and the set current 104,
Corresponds to a constant supply current in ISVM mode. The set currents 105 and 104 are respectively set according to the current value supplied to the DUT.

According to the above-described embodiment, in the VSIM mode, a low output impedance is realized, and the test voltage can be set accurately.
Since the switching circuit selects the first or second differential amplifier, it is possible to cope with DC tests in both the VSIM mode and the ISVM mode.

Although the present invention has been described based on the preferred embodiment, the DC characteristic test apparatus of the present invention is not limited to the configuration of the above-described embodiment, and is not limited to the configuration of the above-described embodiment. A DC characteristic test apparatus having various modifications and changes from the configuration is also included in the scope of the present invention.

[0051]

As described above, in the DC characteristics test apparatus of the present invention, in the VSIM mode, the output section constitutes a complementary emitter follower circuit, and furthermore, the whole constitutes a negative feedback circuit, so that a low output can be obtained. Since the impedance can be realized and the test voltage can be set accurately, the measurement accuracy is high, and the switching circuit selects the first or second differential amplifier, so that the DC test can be performed in both the VSIM mode and the ISVM mode. Can respond.

[Brief description of the drawings]

FIG. 1 is a diagram showing a V of a DC characteristic test apparatus according to an embodiment of the present invention.
Indicates the SIM mode.

FIG. 2 is a specific example of the differential input stage switching amplifier circuit 1 of FIG.

FIG. 3 shows an ISVM mode of the DC characteristic test apparatus of FIG.

FIG. 4 is a block diagram of an IC test apparatus (DC characteristic test apparatus) described in JP-A-7-244125.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 differential input stage switching amplifier circuit 2 voltage source 3 first emitter follower circuit 4 second emitter follower circuit 5 first current mirror circuit 6 second current mirror circuit 7 complementary emitter follower circuit 8 ammeter 9, 10 diode 11th 2 current source 12 first current source 13 voltmeter 14 test terminal 21, 22, 24 constant current source 23 output circuit 41 DUT 42 buffer 43 voltage measurement unit 44 control unit 45 current control unit 46, 47 differential circuit 101 set voltage 102 Test voltage 103 Output voltage 104 Set current (second set current) 105 Set current (first set current) Qn1 to Qn8 NPN transistor Qp1, Qp2 PNP transistor S1 to S5 Switch I5a Reference current (first reference current) I6a Reference current (second reference current) I5b, I6 b Output current ΔIa Difference current (difference current) ΔIb, ΔIc Difference current

Claims (4)

[Claims] 1. A VSIM mode for supplying a constant voltage to a test circuit connected to a test terminal and measuring a current, and an ISV for supplying a constant current and measuring a voltage.
In a DC characteristics test device that operates in one of the M modes, a voltage source that generates a set voltage corresponding to the fixed voltage, the set voltage is connected to a non-inverting terminal, and the test terminal is connected to an inverting terminal. A first differential amplifier having a test terminal connected to a non-inverting terminal and an output terminal fed back to an inverting terminal; and selecting the first differential amplifier in the VSIM mode. And
A switching circuit for selecting the second differential amplifier in the ISVM mode, a current supply circuit for supplying a first reference current from a first power supply voltage, and a recirculation of a second reference current from a second power supply voltage A complementary current follower circuit comprising a pair of emitter followers, wherein the first reference current is circulated from one collector and the second reference current is supplied from the other collector; A first current source that supplies a set current; and a second current source that circulates a second set current. In the VSIM mode, the first reference current and the first reference current are output by the output current from the test circuit. A difference occurs in the second reference current, and in the ISVM mode, the first set current and the second
And supplying the constant current to the test target circuit based on a difference from the set current. 2. The DC characteristics test apparatus according to claim 1, wherein in the VSIM mode, the first differential amplifier operates so that the potentials of the non-inverting terminal and the inverting terminal are equal. 3. The reference current line connected to the test terminal, wherein the current supply circuit and the current circulation circuit are connected to the test terminal.
The current meter is configured by a pair of current mirror circuits having an output-side current line connected to each other, and an ammeter is connected between the output-side current line and a ground.
Or the DC characteristics test apparatus according to 2. 4. The DC characteristic test apparatus according to claim 1, wherein a voltmeter is connected between an output terminal of said second differential amplifier and ground.