JP4967652B2 - Current-voltage amplifier circuit and semiconductor test apparatus - Google Patents

Description

  The present invention relates to a current-voltage amplifier circuit that amplifies or attenuates current and voltage, and more particularly to a current-voltage amplifier circuit suitable for use in an LSI tester or a current-voltage measuring instrument, and a semiconductor test apparatus using the same.

  Conventionally, a current output circuit capable of controlling an output current limit value and an output voltage has been known. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-286808) discloses a circuit that uses five amplifiers (op-amps) and the current output circuit can independently control both the output voltage and the output current limit value. Proposed. However, such a current output circuit has a problem in that the circuit configuration is complicated and the circuit becomes large. In addition, due to the structure of the semiconductor test apparatus, it is difficult to place a circuit in the vicinity of a device under test (hereinafter referred to as “DUT”). For this reason, the current response due to the path resistance and inductance becomes insufficient in the large current region, and the settling time is delayed due to the stray capacitance in the very small current region, which hinders high-speed and high-accuracy measurement.

  In view of this, the present applicant has provided a current amplifying circuit capable of varying the range of the output current with a simple configuration in Japanese Patent Laid-Open No. 2005-192141.

  FIG. 3 is a diagram for explaining the basic configuration of the current amplifier circuit 101 according to Patent Document 2. As shown in FIG. Q1 is an amplifier having two input terminals of an inverting input terminal and a non-inverting input terminal and one output terminal. IN is an input terminal and is connected to the non-inverting input terminal of the amplifier Q1. The resistor R1 has one end connected to the non-inverting input terminal of the amplifier Q1 and the other end connected to the output terminal of the amplifier Q1. The resistor R2 has one end connected to the output terminal of the amplifier Q1, and the other end connected to the inverting input terminal of the amplifier Q1. OUT is an output terminal connected between the inverting input terminal of the amplifier Q1 and the resistor R2.

In the above configuration, the voltage at the input terminal IN is Vi, the current is Ii, the voltage at the output terminal OUT is Vo, and the current is Io. Since no current flows through the non-inverting input terminal and the inverting input terminal of the amplifier Q1, and no potential difference is generated between these two input terminals, the following equations (1) and (2) are established.
Vo = Vi (1)
Vo = R2 × Io + R1 × Ii + Vi (2)
Then, the following expression (3) can be derived.
Io = − (R1 / R2) × Ii (3)
That is, it is possible to configure a current amplifying circuit that amplifies only the current without changing the voltage by using only one amplifier and two resistors. The relationship between the input current and the output current can be set to an arbitrary value by changing the resistance ratio of the resistors R1 and R2. When R2 is larger than R1, it can be used as a current attenuator.

  Then, by connecting the above circuit to the voltage application current measurement output of the semiconductor test apparatus, it becomes possible to measure the output current above the current range. That is, it can be seen that when a predetermined current value is measured in the semiconductor test apparatus, a current R1 / R2 times the measured current flows through the DUT.

FIG. 4 shows a configuration described in Patent Document 2, in which two current amplifying circuits are connected in series and a current limiting function is added. In the current amplifier circuit 101 shown in FIG. 3, feedback is applied when the input signal Ii is subjected to current limitation, and the output voltage rises as a further current flows from the output terminal OUT. In this embodiment, another current amplifying circuit 102 having the same configuration is connected to the previous stage of the current amplifying circuit 101 in FIG. 3 to compensate for the amount of current to avoid an increase in output voltage, and to achieve normal voltage / current limiting. It is made to operate as a circuit.
Japanese Patent Laid-Open No. 2002-286808 JP 2005-192141 A

  However, in the configuration described in Patent Document 2, it is possible to measure an output current exceeding the measurement range, but it is impossible to apply a voltage exceeding the output range. Further, since the relay S1 is disposed between the sensing point, which is the connection position between the resistor R2 and the output terminal of the amplifier Q1, and the DUT, it is difficult to output an accurate voltage.

  Therefore, the present invention provides a current-voltage amplifier circuit that makes it possible to amplify and apply a voltage over a range of a semiconductor test apparatus and measure a current exceeding the range or a minute current, and a semiconductor test apparatus using the same. It is intended to provide.

In order to solve the above problems, a typical configuration of a current-voltage amplifier circuit according to the present invention
An input signal is input to the non-inverting input terminal, a current offset cancellation circuit and a first resistor are connected in series between the non-inverting input terminal and the output terminal, and a second resistor and voltage are connected between the output terminal and the inverting input terminal. A current amplifying circuit including a first amplifier, in which a ratio setting circuit is connected in series, and an output signal line for transmitting a signal to the device under test is connected between the second resistor and the voltage ratio setting circuit;
In the voltage ratio setting circuit, a non-inverting input terminal is connected to the output signal line, an inverting input terminal and an output terminal are short-circuited, and an output terminal is grounded via a series circuit of a third resistor and a fourth resistor, A second amplifier in which an inverting input terminal of the first amplifier is connected between a third resistor and a fourth resistor;
The current offset cancellation circuit has an output terminal connected to the non-inverting input terminal of the first amplifier via the first resistor, the inverting input terminal and the output terminal are short-circuited, and the non-inverting input terminal has a fifth resistor. And a third amplifier connected to the output terminal of the first amplifier via a sixth resistor .

  According to the above configuration, the range of the output current can be expanded and reduced with a simple configuration, and the applied voltage can be amplified with high accuracy. Therefore, by arranging this circuit between the semiconductor test apparatus and the device under test, it is possible to amplify and apply a voltage exceeding the range of the semiconductor test apparatus and measure a current exceeding the range or a minute current.

  When the voltage is amplified by the voltage ratio setting circuit, the voltage is amplified even when no current is flowing, so that an offset current flows. However, according to the current offset cancellation circuit, the offset current can be reduced and a more accurate measurement value can be obtained.

  Moreover, it is preferable that the ratio between the third resistor and the fourth resistor is equal to the ratio between the fifth resistor and the sixth resistor. As a result, the offset current can be almost eliminated, and an accurate value can be obtained without offsetting the measured value.

  In the output signal line, a switch circuit is provided between the second resistor and a sensing point where the output signal line and the non-inverting input terminal of the second amplifier are connected. By arranging the sensing point on the DUT side of the switch circuit provided between the test apparatus and the DUT, the voltage applied to the DUT can be accurately reflected and the voltage can be amplified with high accuracy.

  Further, a second current amplifier circuit may be provided, and the output signal line of the second current amplifier circuit may be connected to the non-inverting input terminal of the first amplifier. When the input signal to the first amplifier is subjected to current limitation, feedback is applied, and the output voltage rises as a further current flows from the output terminal. However, according to the above configuration, the amount of current can be compensated to avoid an increase in output voltage, and the circuit can be operated as a voltage / current limiting circuit.

  According to the present invention, it is possible to amplify and apply a voltage over a range of a semiconductor test apparatus and measure a current over the range or a minute current.

  An embodiment of a current-voltage amplifier circuit according to the present invention will be described. Note that the dimensions, materials, and other specific values such as voltage values, current values, and resistance values shown in the following examples are merely examples for facilitating understanding of the invention, and unless otherwise specified. The invention is not limited.

  FIG. 1 is a diagram for explaining the configuration of a current-voltage amplifier circuit according to this embodiment. The circuit shown in FIG. 1 includes a current amplifier circuit 201, a voltage ratio setting circuit 301, a current offset cancellation circuit 401, and a second current amplifier circuit 501. IN is an input terminal, for example, an input signal is applied from the control unit of the semiconductor test apparatus. OUT is an output terminal that outputs an output signal to, for example, the DUT.

  The current amplifier circuit 201 has two input terminals, an inverting input terminal and a non-inverting input terminal, and one output terminal, and a first amplifier (hereinafter referred to as “amplifier Q1”) in which an input signal is input to the non-inverting input terminal. ), A first resistor (hereinafter referred to as “resistor R1”) connected between the non-inverting input terminal and the output terminal of the amplifier Q1, and a connection between the output terminal and the inverting input terminal of the amplifier Q1. And a signal is sent to the device under test (hereinafter referred to as “DUT”) between the resistor R2 and the inverting input terminal of the amplifier Q1. An output signal line L1 for transmission is connected. The output signal line L1 is provided with a relay S1 as a switch circuit for turning on / off the connection with the DUT. This is referred to as a sensing point P which is a connection position between the resistor R2 and the output terminal of the amplifier Q1.

  In the voltage ratio setting circuit 301, a non-inverting input terminal is connected to the output signal line L1, a inverting input terminal and an output terminal are short-circuited (hereinafter referred to as “amplifier Q2”), and an inverting input of the amplifier Q1. A third resistor (hereinafter referred to as “resistor R3”) whose both ends are connected to the terminal and the ground, and a fourth resistor (hereinafter referred to as “resistor R3”) whose both ends are connected to the inverting input terminal of the amplifier Q1 and the output terminal of the amplifier Q2. Resistor R4]).

  The current offset cancellation circuit 401 includes a third amplifier (hereinafter referred to as “amplifier Q3”) in which an output terminal is connected to the resistor R1, an inverting input terminal and an output terminal are short-circuited, and a non-inverting input terminal of the amplifier Q3 and a ground. And a sixth resistor (hereinafter referred to as “resistor R6”) whose both ends are connected to the non-inverting input terminal of the amplifier Q3 and the output terminal of the amplifier Q1. And).

  The second current amplification circuit 501 has an amplifier Q4 in which an input signal is input to the non-inverting input terminal and the inverting input terminal and the output terminal are short-circuited, and between the non-inverting input terminal and the output terminal of the amplifier Q4. A resistor R7 having both ends connected, and a resistor R8 having both ends connected between the output terminal and the inverting input terminal of the amplifier Q4, and a current amplifier circuit between the resistor R8 and the inverting input terminal of the amplifier Q4 An output signal line for transmitting a signal is connected to 201. The signal output from the second current amplifier circuit 501 is input to the non-inverting input terminal of the amplifier Q1 of the current amplifier circuit 201.

  The operation of the circuit having the above configuration will be described. First, the operation of the second current amplification circuit 501 will be described along the signal flow.

In the second current amplifier circuit 501, the voltage downstream of the resistor R8 is V2, and the current is I2. Since the inverting input terminal and the output terminal are short-circuited, the voltage Vi and the voltage V2 at the input terminal IN are equal.
V2 = Vi (4)
As described in the background art above, V2 can be expressed by the following equation.
V2 = R8 × I2 + R7 × Ii + Vi (5)
Then, the following expression (3) can be derived.
I2 = − (R7 / R8) × Ii (6)
In the present embodiment, the second current amplification circuit 501 sets R7 = R8, and amplifies the current at an equal magnification (Ii = I2). Although the current value is the same, the current can be compensated by the power supply of the amplifier Q4, and the current Ii of the input signal is prevented from being limited (a state in which the current cannot exceed the allowable amount and cannot flow). is doing. As a result, an increase in output voltage can be avoided and the voltage / current limiting circuit can be operated.

  The current amplifier circuit 201 is a circuit obtained by developing the second current amplifier circuit 501 and amplifies the current R1 / R2 times. The sensing point P and the inverting input terminal of the amplifier Q1 are not short-circuited, and the voltage ratio setting circuit 301 is interposed.

In the voltage ratio setting circuit 301, the amplifier Q2 is provided to block the influence of other circuits on the voltage dividing circuit composed of the resistors R3 and R4, and any of the non-inverting input terminal, the inverting input terminal, and the output terminal is provided. The voltage is the same. The voltage V5 divided by the resistors R3 and R4 is input to the non-inverting input terminal of the amplifier Q1. Since the amplifier Q1 amplifies the divided voltage V5 so as to be the same as the voltage V2 input from the second current amplification circuit 501, the voltage V4 applied to the DUT is expressed by the following equation.
V4 = (R3 + R4) / R3 × V2 (7)
That is, by adding the voltage ratio setting circuit 301 to the current amplifier circuit 201, the applied value of the tester voltage can be amplified by (R3 + R4) / (R3) times.

  Furthermore, in this embodiment, relay S1 is arrange | positioned between the sensing point P and resistance R2. Thus, by arranging the sensing point P on the DUT side of the switch circuit, the voltage applied to the DUT can be accurately reflected and the voltage can be amplified with high accuracy.

  Here, the amplification of the voltage is performed even when no current flows. Therefore, a potential difference is generated between the output terminal and the input terminal of the amplifier Q1. Therefore, if the output terminal and the non-inverting input terminal of the amplifier Q1 are simply connected by the resistor R1 (similar to the second current amplification circuit 501), a current flows, and a constant current value is added and measured. End up. This added current is referred to as an offset current.

  The current offset cancellation circuit 401 is provided to reduce or eliminate the offset current. A voltage dividing circuit including resistors R5 and R6 is grounded from the output terminal of the amplifier Q1, and the divided voltage is input to the amplifier Q3. The output terminal of the amplifier Q3 is connected to the non-inverting input terminal of the amplifier Q1 through the resistor R1. As an outline, the voltage increased by the action of the voltage ratio setting circuit 301 is dropped in advance and then input to the resistor R1.

  Even if the offset current is generated, it is possible to measure the current flowing through the DUT by subtracting a predetermined offset current (measured value when the current flowing through the DUT is 0) from the measured value. However, the offset current can be reduced by making the voltage amplified by the current offset cancellation circuit 401 close to the same magnification as in this embodiment, and a more accurate measurement value can be obtained. In particular, the offset current can be almost eliminated by making the voltage dividing ratio composed of the resistors R5 and R6 equal to the voltage dividing ratio composed of the resistors R3 and R4 of the voltage ratio setting circuit 301, and it is not necessary to offset the measured value. Accurate values can be obtained.

According to the above configuration, the gain value of the current-voltage amplifier circuit according to the present embodiment can be expressed as follows.
Current gain = R1 / R2 (8)
Voltage gain = (R3 + R4) / R3 (9)
Current measurement value = (R1 / R2) × ((R3 + R4) / R3) (10)
However, by changing the values of the above R1 to R6 such that R3 = R5 and R4 = R6, it is possible to apply an arbitrary high voltage and measure a current in an arbitrary range.

  That is, since the voltage to be applied can be set by the ratio of only two resistors R3 and R4, it can be amplified with a simple configuration with high accuracy. Therefore, by arranging this circuit between the semiconductor test apparatus and the device under test, a voltage exceeding the range of the semiconductor test apparatus can be amplified and applied. As for the current to be measured, the range of the output current can be set by the ratio of the two resistors R1 and R2, which can be expanded and reduced with a simple configuration, and can measure a current exceeding the measurement range or a minute current. it can.

  The voltage ratio setting circuit 301 may be directly connected to the output terminal of the amplifier Q2 and the inverting input terminal of the amplifier Q1 without providing the resistors R3 and R4. Thereby, the voltage gain becomes equal, but the influence of fluctuations received from the DUT can be cut off and a highly stabilized voltage can be applied. In this case, it goes without saying that the current offset canceling circuit 401 is unnecessary.

  FIG. 2 shows the overall configuration of the semiconductor test apparatus. In FIG. 2, 2 is a semiconductor test apparatus main body, and 3 is a test load on which a DUT is mounted. The semiconductor test apparatus main body 2 includes a power source and a DC parametric measuring instrument.

  In the semiconductor test apparatus, the distance between the semiconductor test apparatus main body 2 and the test load 3 is often as long as 5 to 10 m due to its configuration. Further, the current supplied from the semiconductor test apparatus main body 2 to the test load 3 has a range from a very small current of several μA to a large current of several tens of A and often fluctuates rapidly.

  For example, in a normal state, when a DUT operating with a current of several μA malfunctions, a sudden voltage drop occurs and a current of several tens of A flows. When the DUT is destroyed due to this current, the current value rapidly decreases to several μA.

  When a minute current is supplied from the semiconductor test apparatus main body 2 to the test load 3, the stabilization time becomes longer due to the cable capacity during this period. In addition, when a large current that changes rapidly is applied, the voltage change at the end of the test load 3 becomes gradual due to the inductance of the cable.

  For this reason, the semiconductor test apparatus body 2 is supplied with a current that is not easily affected by the capacitance and inductance of the cable, and the current voltage amplifier circuit of the present invention is mounted on the test load 3 to be amplified or attenuated before being supplied to the DUT. If it supplies, a highly accurate measurement will be attained.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention relates to a current-voltage amplifier circuit that amplifies or attenuates current and voltage, and in particular, can be used as a current-voltage amplifier circuit suitable for use in an LSI tester or a current-voltage measuring instrument, and a semiconductor test apparatus using the same. .

It is a figure explaining the structure of the current voltage amplifier circuit concerning embodiment. It is a figure which shows the whole structure of a semiconductor test apparatus. It is a figure explaining the basic composition of the current amplification circuit 101 concerning a prior art example. It is a figure which shows the structure which connected two current amplifier circuits concerning a prior art example in series, and added the current limiting function.

Explanation of symbols

L1 ... Output signal line P ... Sensing points Q1 to Q4 ... Amplifiers R1 to R6 ... Resistors S1 and S2 ... Relay 2 ... Semiconductor test equipment body 3 ... Test load 101 ... Current amplifier circuit 102 ... Current amplifier circuit 201 ... Current amplifier circuit 301 ... Voltage ratio setting circuit 401 ... Current offset cancellation circuit 501 ... Second current amplification circuit

Claims (5)

An input signal is input to the non-inverting input terminal, a current offset cancellation circuit and a first resistor are connected in series between the non-inverting input terminal and the output terminal, and a second resistor and voltage are connected between the output terminal and the inverting input terminal. A current amplifying circuit including a first amplifier, in which a ratio setting circuit is connected in series, and an output signal line for transmitting a signal to the device under test is connected between the second resistor and the voltage ratio setting circuit;
In the voltage ratio setting circuit, a non-inverting input terminal is connected to the output signal line, an inverting input terminal and an output terminal are short-circuited, and an output terminal is grounded via a series circuit of a third resistor and a fourth resistor, A second amplifier in which an inverting input terminal of the first amplifier is connected between a third resistor and a fourth resistor;
The current offset cancellation circuit has an output terminal connected to the non-inverting input terminal of the first amplifier via the first resistor, the inverting input terminal and the output terminal are short-circuited, and the non-inverting input terminal has a fifth resistor. And a third amplifier connected to the output terminal of the first amplifier via a sixth resistor . 2. The current-voltage amplifier circuit according to claim 1 , wherein a ratio of the third resistor and the fourth resistor is equal to a ratio of the fifth resistor and the sixth resistor . In the output signal line, according to claim 1, wherein during the sensing point and the non-inverting input terminal of said the output signal line and the second amplifier is connected to said second resistor, in that a switching circuit The current-voltage amplifier circuit described. The current-voltage amplifier circuit according to claim 1 , further comprising a second current amplifier circuit, wherein an output signal line of the second current amplifier circuit is connected to a non-inverting input terminal of the first amplifier . A semiconductor test apparatus for conducting an electrical test of a device under test,
A control unit that applies a voltage to the device under test and measures current;
A semiconductor test apparatus comprising the current-voltage amplifier circuit according to claim 1.

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