JP3978672B2 - Voltage applied current measuring instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage application current measuring instrument that measures a current by applying a voltage to a load and an object to be inspected, and relates to a voltage application current measuring instrument that can reduce a phase delay amount and respond quickly.
[0002]
[Prior art]
In a semiconductor inspection apparatus, the quality is determined by driving a load which is an object to be inspected, such as an IC or LSI, with a voltage application current measuring instrument and measuring the current flowing therethrough. Such a voltage application current measuring instrument is described in, for example, Patent Document 1, Patent Document 2, and the like. This will be described below with reference to FIGS. Here, FIG. 5 is a diagram showing a specific configuration of current measurement of the apparatus shown in FIG.
[0003]
In FIG. 4, the D / A converter 10 outputs a voltage. The resistor Ri has one end connected to the output end of the D / A converter 1. The buffer 20 has an input end connected to the other end of the resistor Ri. The resistor R has one end connected to the output end of the buffer 20. In the differential amplifier 30, the inverting input terminal is connected to the other end of the resistor R, and the non-inverting input terminal is grounded. The capacitor C is provided between the non-inverting input terminal and the output terminal of the differential amplifier 30. That is, the differential amplifier 30 and the capacitor C constitute an integrating circuit. The amplifier 40 inputs the output of the differential amplifier 30. The shunt resistor Rs has one end connected to the output end of the amplifier 40. The load 50 connects the other end of the shunt resistor Rs to one end and grounds the other end. The buffer 60 has an input end connected to the other end of the resistor Rs. The resistor Rf has one end connected to the output end of the buffer 60 and the other end connected to the input end of the buffer 20.
[0004]
In FIG. 5, a differential amplifier 71 is connected to both ends of the shunt resistor Rs, and measures the voltage across the shunt resistor Rs. The A / D converter 72 converts the output of the differential amplifier 71 into digital data.
[0005]
The operation of such an apparatus will be described below. The voltage value applied to the load 50 is set in the D / A converter 10, and this set voltage is input to the buffer 20 via the resistor Ri. Further, the voltage of the load 50 is input to the buffer 20 via the buffer 60 and the resistor Rf. That is, the output of the buffer 20 becomes an error voltage that is the difference between the output of the D / A converter 10 and the voltage across the load 50.
[0006]
This error voltage is converted into an error current by the resistor R and input to an integration circuit of the differential amplifier 30 and the capacitor C. Based on the output of this integration circuit, the amplifier 40 gives a set voltage to the load 50 via the shunt resistor Rs.
[0007]
At this time, since the same current as the current flowing through the load 50 flows through the shunt resistor Rs, the voltage across the shunt resistor Rs is measured by the differential amplifier 71 and converted into digital data by the A / D converter 72. In this way, voltage application and current measurement are performed.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-62233
[Patent Document 2]
Japanese Patent Laid-Open No. 2002-286808
[Problems to be solved by the invention]
When the load 50 is capacitive, the response speed itself has to be reduced in order to prevent a phase delay from occurring due to the shunt resistor Rs and the load capacity and instability of the feedback system.
[0011]
Therefore, an object of the present invention is to realize a voltage application current measuring instrument that can reduce the phase lag and respond at high speed.
[0012]
[Means for Solving the Problems]
The invention described in claim 1
In a voltage application current measuring instrument that applies voltage to a load and measures current,
An amplifier for supplying the current;
A shunt resistor provided on each of the positive and negative power supply lines of the amplifier;
Each shunt resistor has a differential amplifier that measures the voltage across the shunt resistor, and the current is measured by subtracting the output of the differential amplifier.
The invention according to claim 2 is the invention according to claim 1,
A subtractor that subtracts the outputs of the differential amplifier;
An A / D converter for converting the output of the subtractor into digital data is provided.
The invention according to claim 3 is the invention according to claim 1 or 2,
A buffer amplifier is inserted between the positive and negative power supplies and the shunt resistor.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the principal part of a first embodiment of the present invention. Here, since the main part shown in FIG. 4 is the same, illustration is abbreviate | omitted.
[0014]
In FIG. 1, an amplifier 80 is provided instead of the amplifier 40 and the shunt resistor Rs illustrated in FIG. 4, and supplies current to the load 50. The buffer amplifiers 81 and 82 receive a positive power supply voltage V + and a negative power supply voltage V−, respectively. The shunt resistors Rs + and Rs− are provided on the negative feedback loops of the buffer amplifiers 81 and 82, respectively. That is, the shunt resistors Rs + and Rs− have one end connected to the output ends of the buffer amplifiers 81 and 82, and the other ends connected to the inverting input terminals of the buffer amplifiers 81 and 82 and the positive and negative power supply terminals of the amplifier 80, respectively. To do. The differential amplifiers 83 and 84 are provided for each of the shunt resistors Rs + and Rs−, and measure the voltage across the shunt resistors Rs + and Rs−. The subtractor 85 subtracts the outputs of the differential amplifiers 83 and 84. The A / D converter 86 converts the output of the subtractor 85 into digital data.
[0015]
The operation of such a device will be described below. Since the overall operation of the voltage application current measuring instrument is the same as that of the conventional example, description thereof is omitted. Here, it is assumed that the input bias current Iin of the amplifier 80 is negligibly small with respect to the load current Iout. Such an amplifier 80 is an FET input type, and can be realized by selecting an input bias current whose fluctuation width due to the load condition, temperature, input signal, etc. is so small as to be negligible with respect to the current to be measured.
[0016]
Consider a case where the load current Iout does not flow through the load 50. The current I1 flowing through the positive power supply is supplied from the buffer amplifier 81 to the amplifier 80 via the shunt resistor Rs +. The current I1 is converted into a voltage by the differential amplifier 83. Similarly, the current I2 flowing to the negative power supply flows from the amplifier 80 to the negative power supply voltage V− via the shunt resistor Rs− and the buffer amplifier 82. The current I2 is converted into a voltage by the differential amplifier 84. Since no current flows through the load 60, the result of subtraction by the subtractor 85 is a value based on the input bias current Iin. However, since the input bias current Iin is negligibly small, the result of the A / D converter 86 by the output from the subtractor 85 becomes zero.
[0017]
When a current flows through the load 50, a load current Iout necessary for the load 50 is supplied from either a positive or negative power source, and a voltage corresponding to the load current Iout is output as a result of the subtractor 85. That is, the relationship is Iout = I1-I2. At this time, even if the magnitudes of the currents I1 and I2 change, the result of subtracting the currents on both the positive side and the negative side becomes zero, so that the measurement of the load current Iout is not affected.
[0018]
As described above, since the shunt resistors Rs + and Rs− are provided on the power supply line of the amplifier 80 and the load current is measured, it is not necessary to provide a shunt resistor in the output stage of the amplifier 80, and the occurrence of the phase delay is very small. can do. As a result, the response of the voltage setting loop can be speeded up.
[0019]
Next, a second embodiment will be described with reference to FIG. Here, the same components as those shown in FIG.
[0020]
In FIG. 2, buffer amplifiers 87 and 88 are provided in place of the buffer amplifiers 81 and 82, respectively, and an output end and an inverting input terminal are connected to one end of the shunt resistors Rs + and Rs−.
[0021]
A third embodiment will be described with reference to FIG. Here, the same components as those shown in FIG.
[0022]
In FIG. 3, amplifiers 89 and 90 are provided in place of the amplifier 80, and the other ends of the shunt resistors Rs + and Rs− are connected to positive and negative power supply terminals. The output of the amplifier 89 is input to the amplifier 90, and the output of the amplifier 90 is supplied to the load 50. The amplifier 89 is a low input bias current fluctuation amplifier. That is, the amplifiers 89 and 90 may be combined to form one amplifier.
[0023]
The operation of the apparatus shown in FIGS. 2 and 3 is the same as that of the apparatus shown in FIG.
[0024]
The present invention is not limited to this, and the configuration in which the buffer amplifiers 81, 82, 87, 88 are provided in order to stabilize the voltage of the amplifier 80 is shown. However, the buffer amplifiers 81, 82, 87, 88, A configuration without 88 is also possible. In addition, although the configuration in which the voltage is obtained by the A / D converter 86 after the output of the subtractor 85 is shown, the voltage value may be detected by an analog voltmeter or the like. Moreover, although the structure which provided the subtractor 85 was shown, an A / D converter is provided for every output of the differential amplifiers 83 and 84, and the output of an A / D converter is subtracted by a calculating part, and load current is calculated | required It may be configured.
[0025]
【The invention's effect】
According to the present invention, since the shunt resistor is provided on the power supply line of the amplifier and the load current is measured, it is not necessary to provide the shunt resistor in the output stage of the amplifier, and the occurrence of the phase delay can be greatly reduced. . As a result, there is an effect that the response of the voltage setting loop can be speeded up.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram showing a first embodiment of the present invention;
FIG. 2 is a main part configuration diagram showing a second embodiment of the present invention;
FIG. 3 is a block diagram showing the principal part of a third embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a conventional voltage application current measuring instrument.
5 is a diagram showing a specific configuration for current measurement of the apparatus shown in FIG. 4; FIG.
[Explanation of symbols]
60 Load 80, 89, 90 Amplifier 81, 82, 87, 88 Buffer amplifier 83, 84 Differential amplifier 85 Subtractor 86 A / D converter Rs +, Rs- Shunt resistance

Claims (3)

In a voltage application current measuring instrument that applies voltage to a load and measures current,
An amplifier for supplying the current;
A shunt resistor provided on each of the positive and negative power supply lines of the amplifier;
A voltage application current measuring instrument comprising a differential amplifier for measuring a voltage across the shunt resistor for each shunt resistor, and measuring the current by subtracting the output of the differential amplifier. A subtractor that subtracts the outputs of the differential amplifier;
The voltage applied current measuring device according to claim 1, further comprising an A / D converter for converting the output of the subtractor into digital data. 3. The voltage application current measuring instrument according to claim 1, wherein a buffer amplifier is inserted between the positive and negative power supplies and the shunt resistor.

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