CA1228176A - Electronic device measurement apparatus - Google Patents
Electronic device measurement apparatusInfo
- Publication number
- CA1228176A CA1228176A CA000491892A CA491892A CA1228176A CA 1228176 A CA1228176 A CA 1228176A CA 000491892 A CA000491892 A CA 000491892A CA 491892 A CA491892 A CA 491892A CA 1228176 A CA1228176 A CA 1228176A
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- Canada
- Prior art keywords
- voltage
- terminal
- electronic device
- resistor
- amplifier
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/26—Testing of individual semiconductor devices
- G01R31/2601—Apparatus or methods therefor
- G01R31/2603—Apparatus or methods therefor for curve tracing of semiconductor characteristics, e.g. on oscilloscope
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Current Or Voltage (AREA)
- Testing Of Individual Semiconductor Devices (AREA)
- Amplifiers (AREA)
Abstract
ABSTRACT
A voltage divider and a current detecting resistor are connected between both terminals of a device under test (DUT), and three buffer amplifiers are connected to both the terminals of the DUT and an output terminal of the voltage divider. A voltage from a floating power supply is applied between one terminal of the DUT and a common junction of the current detecting resistor and the voltage divider. Since a current flowing through the voltage divider does not flow through the current detecting resistor, a voltage across the current detecting resistor is proportional to a current flowing through the DUT. An operational circuit receives output signals from the three buffer amplifiers to obtain a voltage proportional to a voltage across the DUT. A characteristic of the DUT is measured in accordance with the voltage across the current detecting resistor and the voltage from the operational circuit.
A voltage divider and a current detecting resistor are connected between both terminals of a device under test (DUT), and three buffer amplifiers are connected to both the terminals of the DUT and an output terminal of the voltage divider. A voltage from a floating power supply is applied between one terminal of the DUT and a common junction of the current detecting resistor and the voltage divider. Since a current flowing through the voltage divider does not flow through the current detecting resistor, a voltage across the current detecting resistor is proportional to a current flowing through the DUT. An operational circuit receives output signals from the three buffer amplifiers to obtain a voltage proportional to a voltage across the DUT. A characteristic of the DUT is measured in accordance with the voltage across the current detecting resistor and the voltage from the operational circuit.
Description
~28~7~ , ELECTRONIC DEVICE MEASUREMENT APPARATUS
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring characteristics of electronic devices, such as transistors, diodes, etc.
Known measurement devices will be described in detail hereinbelow.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention there is provided an electronic device measurement apparatus, comprising: voltage supply means for supplying a voltage between first and second terminals of an electronic device under test: a current detecting resistor inserted between said voltage supply means and the second terminal of said electronic device; a voltage divider connected between one terminal of said current detecting resistor adjacent to said voltage supply means and the first terminal of said electronic device; a first buffer amplifier having an input terminal connected to an output terminal of said voltage divider; a second buffer amplifier ~213~
having an input terminal connected to the second terminal of said electronic device; and an operational circuit to receive output signals from said first and second buffer amplifiers and a signal at said one terminal of said current detecting resistor; wherein a characteristic of said electronic device is measured in accordance with a voltage across said current detecting resistor and an output signal from said operational circuit.
Since the voltage divider for dividing the voltage between the first and second terminals of the DUTY is not connected to the common junction of the second terminal of the DUTY and the current detecting resistor and the input impedances of the buffer amplifiers are very high, only the current flowing between the first and second terminals of the DUTY flows through the current detecting resistor and this current can be detected accurately. As the result that the first buffer amplifier receives the first terminal voltage divided by the voltage divider, this first buffer amplifier does not receive the high voltage and it is not needed to be floated. When the voltage divider divides the voltage between the first and second terminals of the DUTY an error voltage occurs because of the voltage across the current detecting resistor. This error voltage is compensated by applying the output signals from the first, second and third buffer amplifiers to the operational circuit. The second buffer amplifier prevents I ~22~7~
the current at the second terminal of the DUTY from flowing into operational circuit, and the third buffer amplifier prevents the current from flowing from the power voltage source of the second buffer amplifier through the output terminal thereof and the operational circuit to the power voltage source of the DUTY Thus, the measurement can be accomplished accurately.
It is, therefore, an object of the present invention to provide an apparatus which measures characteristics of electronic devices accurately.
It is another object of the present invention to provide an electronic device measurement apparatus which detects accurately a current flowing a DUTY regardless of a voltage divider connected to the DUTY
It is a further object of the present invention to provide an electronic device measurement apparatus which does not need a complex and expensive floating ; buffer amplifier.
Other objects and advantages of the present invention will become apparent to those having ordinary skill in the art when taken in conjunction with the accompanying drawings.
DRAWINGS
FIG. 1 shows a block diagram of a conventional electronic device measurement apparatus;
FIG. 2 shows a simplified block diagram of I ~28~7~
another conventional electronic device measurement apparatus;
FIG. 3 shows a simplified block diagram of a third conventional electronic device measurement apparatus; and FIG. 4 shows a circuit diagram of a part of a electronic device measurement apparatus according to the present invention.
RETAILED DESCRIPTION OF THE INVENTION
An electronic device measurement apparatus called generally a curve trace is useful to measure characteristics of electronic devices, such as transistors, diodes, etc. A typical one of conventional electronic device measurement apparatus is illustrated in FIG. 1, I wherein an AC voltage from a line source is applied through a switch 10 to a power supply circuit 12 and a variable transformer 14. The power supply circuit 12 produces do voltages for each circuit of the measurement apparatus, and the variable transformer 14 supplies an AC
voltage having a controlled amplitude to a primary winding of a transformer 16. A plurality of taps are provided at a secondary winding of the transformer 16, and one of these taps excluding the lowest position tap is selected by a switch 18. A diode 20 is a half-wave rectifier which \
- 5 - ~22~7~
rectifies the AC voltage from the switch 18. These elements 10-20 construct a floating collector supply circuit 21. The cathode voltage of the diode 20 is applied to a first terminal of a device under test (DUTY), S e.g., the collector of a transistor 26 through a load resistor 24 selected by a switch 22. The base of the transistor 26 receives a step bias signal from a bias supply circuit 28 and the emitter thereof as a second terminal is grounded. The lowest position tap of the secondary winding of the transformer 16 is connected to the emitter of the transistor 26 through a collector current detecting resistor 32 selected by a switch 30.
A voltage divider 36 selected by a switch 34 divides the collector voltage Vc of the transistor 26, and the divided voltage is applied to a horizontal deflection plate of a cathode ray tube (CRT) 40 through an amplifier 38 having a high input impedance. A differential amplifier operettas as a high input impedance voltage detector which detects a voltage across a resistor 32 (being substantially pro-portion Al to the collector current Icy and applies into a vertical deflection plate of the CUT 40. Thus, the CRT 40 may display the Vc-Ic characteristic curve of the transistor 26. In FIG. 1, the DUTY 26 is the common emitter transistor. However, any electrode of the transistor may be grounded, and the DUTY may be other electronic devices, such as a diode. In any cases, the voltage-current 6 ~22~3~7~i characteristic of the DUTY may be displayed on the CRT 40.
On the other hand, the switches 30 and 34 are controlled in accordance with a desired measurement range.
A horizontal-axis size of the display is determined by a dividing ratio of the voltage divider 36 selected by the switch 34, while a vertical-axis size thereof is determined by a value of the resistor 32 selected by the switch 30.
The maximum voltage to be applied to the DUTY or the measurement range is determined by the adjustment of the variable transformer 14 and the selection of the switch 18. Thus, it is necessary to select the resistor 32 having the small value when measuring a large current flowing through the DUTY and it is necessary to select the voltage divider 36 having the large dividing ratio when measuring a large voltage across the DUTY
As described herein before, the voltage divider 36 is necessary to adjust the measurement range. As a result of the voltage divider 36, the current flowing through the selected resistor 32 is the sum of the collector current of the transistor 26 and the current flowing through the voltage divider 36. It should be noted that the base current of the transistor 26 flows through ground to the bias supply circuit 28 and does not flow through the resistor 32, because the output current value of the collector supply circuit 21 (at the cathode of the diode 20) is equal to the input current value thereof (at the I ~228~
lowest position terminal of the transformer 16). Thus, the voltage across the resistor 32 is not directly proportional to the collector current of the transistor 26 and leads to error in the measurement result.
An another conventional measurement apparatus overcoming this measurement error is Tektronix curve tracer model 576, and a simplified block diagram is shown in FIG.
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring characteristics of electronic devices, such as transistors, diodes, etc.
Known measurement devices will be described in detail hereinbelow.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention there is provided an electronic device measurement apparatus, comprising: voltage supply means for supplying a voltage between first and second terminals of an electronic device under test: a current detecting resistor inserted between said voltage supply means and the second terminal of said electronic device; a voltage divider connected between one terminal of said current detecting resistor adjacent to said voltage supply means and the first terminal of said electronic device; a first buffer amplifier having an input terminal connected to an output terminal of said voltage divider; a second buffer amplifier ~213~
having an input terminal connected to the second terminal of said electronic device; and an operational circuit to receive output signals from said first and second buffer amplifiers and a signal at said one terminal of said current detecting resistor; wherein a characteristic of said electronic device is measured in accordance with a voltage across said current detecting resistor and an output signal from said operational circuit.
Since the voltage divider for dividing the voltage between the first and second terminals of the DUTY is not connected to the common junction of the second terminal of the DUTY and the current detecting resistor and the input impedances of the buffer amplifiers are very high, only the current flowing between the first and second terminals of the DUTY flows through the current detecting resistor and this current can be detected accurately. As the result that the first buffer amplifier receives the first terminal voltage divided by the voltage divider, this first buffer amplifier does not receive the high voltage and it is not needed to be floated. When the voltage divider divides the voltage between the first and second terminals of the DUTY an error voltage occurs because of the voltage across the current detecting resistor. This error voltage is compensated by applying the output signals from the first, second and third buffer amplifiers to the operational circuit. The second buffer amplifier prevents I ~22~7~
the current at the second terminal of the DUTY from flowing into operational circuit, and the third buffer amplifier prevents the current from flowing from the power voltage source of the second buffer amplifier through the output terminal thereof and the operational circuit to the power voltage source of the DUTY Thus, the measurement can be accomplished accurately.
It is, therefore, an object of the present invention to provide an apparatus which measures characteristics of electronic devices accurately.
It is another object of the present invention to provide an electronic device measurement apparatus which detects accurately a current flowing a DUTY regardless of a voltage divider connected to the DUTY
It is a further object of the present invention to provide an electronic device measurement apparatus which does not need a complex and expensive floating ; buffer amplifier.
Other objects and advantages of the present invention will become apparent to those having ordinary skill in the art when taken in conjunction with the accompanying drawings.
DRAWINGS
FIG. 1 shows a block diagram of a conventional electronic device measurement apparatus;
FIG. 2 shows a simplified block diagram of I ~28~7~
another conventional electronic device measurement apparatus;
FIG. 3 shows a simplified block diagram of a third conventional electronic device measurement apparatus; and FIG. 4 shows a circuit diagram of a part of a electronic device measurement apparatus according to the present invention.
RETAILED DESCRIPTION OF THE INVENTION
An electronic device measurement apparatus called generally a curve trace is useful to measure characteristics of electronic devices, such as transistors, diodes, etc. A typical one of conventional electronic device measurement apparatus is illustrated in FIG. 1, I wherein an AC voltage from a line source is applied through a switch 10 to a power supply circuit 12 and a variable transformer 14. The power supply circuit 12 produces do voltages for each circuit of the measurement apparatus, and the variable transformer 14 supplies an AC
voltage having a controlled amplitude to a primary winding of a transformer 16. A plurality of taps are provided at a secondary winding of the transformer 16, and one of these taps excluding the lowest position tap is selected by a switch 18. A diode 20 is a half-wave rectifier which \
- 5 - ~22~7~
rectifies the AC voltage from the switch 18. These elements 10-20 construct a floating collector supply circuit 21. The cathode voltage of the diode 20 is applied to a first terminal of a device under test (DUTY), S e.g., the collector of a transistor 26 through a load resistor 24 selected by a switch 22. The base of the transistor 26 receives a step bias signal from a bias supply circuit 28 and the emitter thereof as a second terminal is grounded. The lowest position tap of the secondary winding of the transformer 16 is connected to the emitter of the transistor 26 through a collector current detecting resistor 32 selected by a switch 30.
A voltage divider 36 selected by a switch 34 divides the collector voltage Vc of the transistor 26, and the divided voltage is applied to a horizontal deflection plate of a cathode ray tube (CRT) 40 through an amplifier 38 having a high input impedance. A differential amplifier operettas as a high input impedance voltage detector which detects a voltage across a resistor 32 (being substantially pro-portion Al to the collector current Icy and applies into a vertical deflection plate of the CUT 40. Thus, the CRT 40 may display the Vc-Ic characteristic curve of the transistor 26. In FIG. 1, the DUTY 26 is the common emitter transistor. However, any electrode of the transistor may be grounded, and the DUTY may be other electronic devices, such as a diode. In any cases, the voltage-current 6 ~22~3~7~i characteristic of the DUTY may be displayed on the CRT 40.
On the other hand, the switches 30 and 34 are controlled in accordance with a desired measurement range.
A horizontal-axis size of the display is determined by a dividing ratio of the voltage divider 36 selected by the switch 34, while a vertical-axis size thereof is determined by a value of the resistor 32 selected by the switch 30.
The maximum voltage to be applied to the DUTY or the measurement range is determined by the adjustment of the variable transformer 14 and the selection of the switch 18. Thus, it is necessary to select the resistor 32 having the small value when measuring a large current flowing through the DUTY and it is necessary to select the voltage divider 36 having the large dividing ratio when measuring a large voltage across the DUTY
As described herein before, the voltage divider 36 is necessary to adjust the measurement range. As a result of the voltage divider 36, the current flowing through the selected resistor 32 is the sum of the collector current of the transistor 26 and the current flowing through the voltage divider 36. It should be noted that the base current of the transistor 26 flows through ground to the bias supply circuit 28 and does not flow through the resistor 32, because the output current value of the collector supply circuit 21 (at the cathode of the diode 20) is equal to the input current value thereof (at the I ~228~
lowest position terminal of the transformer 16). Thus, the voltage across the resistor 32 is not directly proportional to the collector current of the transistor 26 and leads to error in the measurement result.
An another conventional measurement apparatus overcoming this measurement error is Tektronix curve tracer model 576, and a simplified block diagram is shown in FIG.
2. FIG. 2 shows only improved parts of the block diagram of Fog. 1. In FIG. 2, a first voltage divider 36 con-sitting of resistors 44 and 46 is connected between the collector of the transistor 26 and the collector supply side of the current detecting resistor 32, and a second voltage divider 52 consisting of resistors 48 and 50 is-connected in parallel with the resistor 32. Divided out-puts from the first and second voltage dividers 36 and 52 are applied to a differential amplifier 54. It should be noted that the value of the resistor 32 and the dividing ratio of the first voltage divider 36 are variable. Since a current flowing through the voltage divider 36 flows through the voltage divider 52 instead of the resistor 32 because values of the resistors 48 and 50 are very large, this current does not lead to the measurement error. A
voltage across the first voltage divider 36 does not correspond to the voltage between the collector and the emitter of the transistor 26 (the first and second terminals of the DUTY because of the voltage across the Jo -8- ~28~7~
resistor 32, but an output voltage from the differential amplifier 54 is not affected by the voltage across the resistor 32 because a dividing ratio of the second voltage divider 52 is set to be equal to that of the first voltage divider 36. In this prior art, the values of the resistors 48 and 50 are set to be very large with respect to the value of the resistor 32. However, when the resistor 32 of a high resistance is selected by the switch 30 for measuring a small current, a small part of the collector current of the transistor 26 is shunted into the second voltage divider 52. Thus, the error occurs in the measurement result.
This measurement error is overcome by Tektronix curve tracer model 577 of which a main part is shown in FIG. 3. In FIG. 3, the collector of the transistor 26 (the first terminal of the DUTY is connected to a buffer amplifier 56, and an output voltage therefrom is applied to the voltage divider 36. Since an input impedance of the buffer amplifier 56 is very high, only the collector current of the transistor 26 flows through the current detecting resistor 32. Moreover, the divided output voltage from the voltage divider 36 is accurately proportional to the collector voltage of the transistor 26. There are various kinds of Duty including a high voltage transistor, so that an input voltage of the buffer -9- 1.;22~3~L7~
amplifier 56 changes in a wide range. Consequently, the buffer amplifier 56 should be floated. The floating amplifier needs a special power supply, a chopping amplifier, etc. and the measurement apparatus becomes complex and expensive in construction.
Referring to FIG. I, there is shown a circuit diagram of a part of a preferred embodiment according to the present invention wherein the voltage detector for detecting the voltage across the DUTY This embodiment uses Kelvin sensing technique for avoiding that the measurement result is affected by contact resistances when the DUTY is connected to the electronic device measurement apparatus. The collector of the transistor 26 as the DUTY is touched to contacts 58 and 60 and the emitter thereof is touched to contacts 62 and 64. This is accomplished by putting the electrode of the transistor between the two contacts. The contacts 58 and 60 correspond to the first terminal of the 8~L7~
DUTY and the contacts 62 and 64 correspond to the second terminal thereof. The contact 58 is connected through the selected load resistor 24 to one electrode of a floating collector supply 21, and the contact 62 is connected through the selected current detecting resistor 32 to the other electrode of the floating collector supply 21.
The collector supply 21 may be the circuit consisting of the transformer 16, the switch 18 and the diode 20 shown in FIG. 1. The contact 62 is -grounded for the base current path. The voltage divider 36 consisting of resistors 44 and 46 is connected between the contact 60 and the collector supply side of the resistor 32. The resistors 44 and 46 may be changed by the switch 34 of FIG. 1.
The dividing ratio of the voltage divider 36 is variable and defined as n. Thus, R44=(n-l)R46, wherein R44 and R46 represent the values of the resistors 44 and 46, respectively.
An output terminal of the voltage divider 36 is connected to an input terminal of a first buffer amplifier 66, the contact 64 is connected to an input terminal of a second buffer 28~
amplifier 68, and the collector supply side of the resistor 32 is connected to an input terminal of a third buffer amplifier 70. These buffer amplifiers are, for example, operational amplifiers connected as voltage followers. Since currents flowing through the contacts 60 and 64 are much less than currents flowing through the contacts 58 and 62 because of the high resistance of the voltage divider 36 and the high input impedances of the buffer amplifiers, the voltages across the DUTY can be detected without being affected by the contact resistances. An output voltage from the buffer amplifier 66 is divided by resistors 72 and 74 and applied to a non-inverting input terminal of a buffer amplifier 76. The output voltages from the buffer amplifiers 68 and 70 are applied to an inverting input terminallof the buffer amplifier 76 through resistors 78 and 80, respectively. A
feedback resistor 82 is inserted between an output terminal and the inverting input terminal of the buffer amplifier 76. The resistances of the resistors 78 and 80 are changed in accordance with the dividing ratio of the voltage divider 36 as ,, ~228~7~;
described hereinafter. These resistors 72, 74, 78 through 82 and the operational amplifier 76 construct an operational circuit. Resistors 84 and 86 are inserted between the contacts pa and 60 and between the contacts 62 and 64, respectively, the values of the resistors 84 and 86 being much larger than the contact resistance. Thus, voltage levels of the contacts 58 and 60 are equal to each other and voltage levels of the contacts 62 and 64 are equal to each other, even if the DUTY is not connected. The output terminal of the amplifier 76 may be connected to the amplifier 38 of FIG. 1 and both the terminal of the resistor 32 may be connected to the differential amplifier 42 of FIG.
1.
A current of the voltage divider 36 flows from the collector supply 21 through the contacts 58 and 60 (a small part of the current flows through the resistor 84) and the voltage divider 36 to the collector supply 21. A current for the DUTY
26 flows from the collector supply 21 through the contact 58, the DUTY 26 (the collector-emitter path of the transistor 26), the contact 62 and the 8~7~i resistor 32 to the collector supply 21. Thus, the current flowing through the resistor 32 is not affected by the voltage divider 36. Since the current from the bias supply circuit 28 flows through the base-emitter junction of the transistor 26, the contact 62 and ground to the bias supply circuit 28, this current does not flow through the resistor 32. Consequently, the current flowing through the resistor 32 is only the current flowing between the first and second terminals of the DUTY
26, so that the current of the DUTY can be detected accurately.
The voltage at the upper terminal of the voltage divider 36 is the voltage at the first terminal of the Depth collector of the transistor 26), however, the voltage at the lower terminal of the voltage divider 36 is the voltage at the second terminal of the Depth emitter of the transistor . 26) offset by the voltage across the contact resistance of the contact 62 and the voltage across the resistor 32. Assuming that the voltages at the upper and lower terminals of the voltage divider 36 are respectively Vc and VG and the voltage at the second terminal of the DUTY is VEX the divided output voltage ED of the voltage divider 36 is as follows:
VD=(VC-vG)/n+vG
Since the gains of all the buffer amplifiers 66, 68 and 70 are +1, the output voltage V0 is as follows:
Vo={R74/(R72+R74)}{R82/(R78//R80)+1}VD
-(R82/R78)vE
-(R82/R8o)vG
wherein R72 through R82 represent the values of the resistors 72 through 82, respectively, and R78//R80 represents the parallel resistance of the resistors 78 and 80. Assuming that R72=R74=R82, R78=nR72 and R80={n/(n-l)}R72, V0 is as follows:
Vo=(Vc-VE)/n Thus, the voltage V0 is the voltage between the first and second terminals divided by n. The operational circuit) compensates the voltages across the contact and the resistor 32.
The buffer amplifier 70 is provided instead of directly connecting the lower terminal of the ~L2~8~7~
, ,~, Jo --aye--resistor 80 to the right side of the resistor 32, so that the current from the power terminal of the buffer amplifier 68 is prevented from flowing through the resistor 32. Therefore, the voltage between the first and second terminals of the DUTY
and the current flowing through the DUTY can be measured accurately with a simple construction.
It should be noted that the buffer amplifiers may be emitter follow amplifiers or voltage follow amplifiers.
While I have shown and described herein the preferred embodiment of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from our invention in its broader aspects. Therefore, the scope of the present invention should be determined only by the following claims.
voltage across the first voltage divider 36 does not correspond to the voltage between the collector and the emitter of the transistor 26 (the first and second terminals of the DUTY because of the voltage across the Jo -8- ~28~7~
resistor 32, but an output voltage from the differential amplifier 54 is not affected by the voltage across the resistor 32 because a dividing ratio of the second voltage divider 52 is set to be equal to that of the first voltage divider 36. In this prior art, the values of the resistors 48 and 50 are set to be very large with respect to the value of the resistor 32. However, when the resistor 32 of a high resistance is selected by the switch 30 for measuring a small current, a small part of the collector current of the transistor 26 is shunted into the second voltage divider 52. Thus, the error occurs in the measurement result.
This measurement error is overcome by Tektronix curve tracer model 577 of which a main part is shown in FIG. 3. In FIG. 3, the collector of the transistor 26 (the first terminal of the DUTY is connected to a buffer amplifier 56, and an output voltage therefrom is applied to the voltage divider 36. Since an input impedance of the buffer amplifier 56 is very high, only the collector current of the transistor 26 flows through the current detecting resistor 32. Moreover, the divided output voltage from the voltage divider 36 is accurately proportional to the collector voltage of the transistor 26. There are various kinds of Duty including a high voltage transistor, so that an input voltage of the buffer -9- 1.;22~3~L7~
amplifier 56 changes in a wide range. Consequently, the buffer amplifier 56 should be floated. The floating amplifier needs a special power supply, a chopping amplifier, etc. and the measurement apparatus becomes complex and expensive in construction.
Referring to FIG. I, there is shown a circuit diagram of a part of a preferred embodiment according to the present invention wherein the voltage detector for detecting the voltage across the DUTY This embodiment uses Kelvin sensing technique for avoiding that the measurement result is affected by contact resistances when the DUTY is connected to the electronic device measurement apparatus. The collector of the transistor 26 as the DUTY is touched to contacts 58 and 60 and the emitter thereof is touched to contacts 62 and 64. This is accomplished by putting the electrode of the transistor between the two contacts. The contacts 58 and 60 correspond to the first terminal of the 8~L7~
DUTY and the contacts 62 and 64 correspond to the second terminal thereof. The contact 58 is connected through the selected load resistor 24 to one electrode of a floating collector supply 21, and the contact 62 is connected through the selected current detecting resistor 32 to the other electrode of the floating collector supply 21.
The collector supply 21 may be the circuit consisting of the transformer 16, the switch 18 and the diode 20 shown in FIG. 1. The contact 62 is -grounded for the base current path. The voltage divider 36 consisting of resistors 44 and 46 is connected between the contact 60 and the collector supply side of the resistor 32. The resistors 44 and 46 may be changed by the switch 34 of FIG. 1.
The dividing ratio of the voltage divider 36 is variable and defined as n. Thus, R44=(n-l)R46, wherein R44 and R46 represent the values of the resistors 44 and 46, respectively.
An output terminal of the voltage divider 36 is connected to an input terminal of a first buffer amplifier 66, the contact 64 is connected to an input terminal of a second buffer 28~
amplifier 68, and the collector supply side of the resistor 32 is connected to an input terminal of a third buffer amplifier 70. These buffer amplifiers are, for example, operational amplifiers connected as voltage followers. Since currents flowing through the contacts 60 and 64 are much less than currents flowing through the contacts 58 and 62 because of the high resistance of the voltage divider 36 and the high input impedances of the buffer amplifiers, the voltages across the DUTY can be detected without being affected by the contact resistances. An output voltage from the buffer amplifier 66 is divided by resistors 72 and 74 and applied to a non-inverting input terminal of a buffer amplifier 76. The output voltages from the buffer amplifiers 68 and 70 are applied to an inverting input terminallof the buffer amplifier 76 through resistors 78 and 80, respectively. A
feedback resistor 82 is inserted between an output terminal and the inverting input terminal of the buffer amplifier 76. The resistances of the resistors 78 and 80 are changed in accordance with the dividing ratio of the voltage divider 36 as ,, ~228~7~;
described hereinafter. These resistors 72, 74, 78 through 82 and the operational amplifier 76 construct an operational circuit. Resistors 84 and 86 are inserted between the contacts pa and 60 and between the contacts 62 and 64, respectively, the values of the resistors 84 and 86 being much larger than the contact resistance. Thus, voltage levels of the contacts 58 and 60 are equal to each other and voltage levels of the contacts 62 and 64 are equal to each other, even if the DUTY is not connected. The output terminal of the amplifier 76 may be connected to the amplifier 38 of FIG. 1 and both the terminal of the resistor 32 may be connected to the differential amplifier 42 of FIG.
1.
A current of the voltage divider 36 flows from the collector supply 21 through the contacts 58 and 60 (a small part of the current flows through the resistor 84) and the voltage divider 36 to the collector supply 21. A current for the DUTY
26 flows from the collector supply 21 through the contact 58, the DUTY 26 (the collector-emitter path of the transistor 26), the contact 62 and the 8~7~i resistor 32 to the collector supply 21. Thus, the current flowing through the resistor 32 is not affected by the voltage divider 36. Since the current from the bias supply circuit 28 flows through the base-emitter junction of the transistor 26, the contact 62 and ground to the bias supply circuit 28, this current does not flow through the resistor 32. Consequently, the current flowing through the resistor 32 is only the current flowing between the first and second terminals of the DUTY
26, so that the current of the DUTY can be detected accurately.
The voltage at the upper terminal of the voltage divider 36 is the voltage at the first terminal of the Depth collector of the transistor 26), however, the voltage at the lower terminal of the voltage divider 36 is the voltage at the second terminal of the Depth emitter of the transistor . 26) offset by the voltage across the contact resistance of the contact 62 and the voltage across the resistor 32. Assuming that the voltages at the upper and lower terminals of the voltage divider 36 are respectively Vc and VG and the voltage at the second terminal of the DUTY is VEX the divided output voltage ED of the voltage divider 36 is as follows:
VD=(VC-vG)/n+vG
Since the gains of all the buffer amplifiers 66, 68 and 70 are +1, the output voltage V0 is as follows:
Vo={R74/(R72+R74)}{R82/(R78//R80)+1}VD
-(R82/R78)vE
-(R82/R8o)vG
wherein R72 through R82 represent the values of the resistors 72 through 82, respectively, and R78//R80 represents the parallel resistance of the resistors 78 and 80. Assuming that R72=R74=R82, R78=nR72 and R80={n/(n-l)}R72, V0 is as follows:
Vo=(Vc-VE)/n Thus, the voltage V0 is the voltage between the first and second terminals divided by n. The operational circuit) compensates the voltages across the contact and the resistor 32.
The buffer amplifier 70 is provided instead of directly connecting the lower terminal of the ~L2~8~7~
, ,~, Jo --aye--resistor 80 to the right side of the resistor 32, so that the current from the power terminal of the buffer amplifier 68 is prevented from flowing through the resistor 32. Therefore, the voltage between the first and second terminals of the DUTY
and the current flowing through the DUTY can be measured accurately with a simple construction.
It should be noted that the buffer amplifiers may be emitter follow amplifiers or voltage follow amplifiers.
While I have shown and described herein the preferred embodiment of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from our invention in its broader aspects. Therefore, the scope of the present invention should be determined only by the following claims.
Claims (4)
1. An electronic device measurement apparatus, comprising:
voltage supply means for supplying a voltage between first and second terminals of an electronic device under test;
a current detecting resistor inserted between said voltage supply means and the second terminal of said electronic device;
a voltage divider connected between one terminal of said current detecting resistor adjacent to said voltage supply means and the first terminal of said electronic device;
a first buffer amplifier having an input terminal connected to an output terminal of said voltage divider;
a second buffer amplifier having an input terminal connected to the second terminal of said electronic device; and an operational circuit to receive output signals from said first and second buffer amplifiers and a signal at said one terminal of said current detecting resistor;
wherein a characteristic of said electronic device is measured in accordance with a voltage across said current detecting resistor and an output signal from said operational circuit.
voltage supply means for supplying a voltage between first and second terminals of an electronic device under test;
a current detecting resistor inserted between said voltage supply means and the second terminal of said electronic device;
a voltage divider connected between one terminal of said current detecting resistor adjacent to said voltage supply means and the first terminal of said electronic device;
a first buffer amplifier having an input terminal connected to an output terminal of said voltage divider;
a second buffer amplifier having an input terminal connected to the second terminal of said electronic device; and an operational circuit to receive output signals from said first and second buffer amplifiers and a signal at said one terminal of said current detecting resistor;
wherein a characteristic of said electronic device is measured in accordance with a voltage across said current detecting resistor and an output signal from said operational circuit.
2. An electronic device measurement apparatus according to claim 1 further includes a third buffer amplifier inserted between said one terminal of said current detecting resistor and said operational circuit.
3. An electronic device measurement apparatus accordance to claim 1, wherein said operational circuit is an operational amplifier circuit including an operational amplifier, a feedback resistor connected between output and inverting input terminals of said operational amplifier, a voltage divider connected between an output terminal of said first buffer amplifier and an non-inverting input terminal of said operational amplifier, a first input resistor connected between an output terminal of said second buffer amplifier and the inverting input terminal of said operational amplifier and a second input resistor inserted between said one terminal of said current detecting resistor and the inverting terminal of said operational amplifier.
4. An electronic device measurement apparatus accordance to claim 2, wherein said operational circuit is an operational amplifier circuit including an operational amplifier, a feedback resistor connected between output and inverting input terminals of said operational amplifier, a voltage divider connected between an output terminal of said first buffer amplifier and an non-inverting input terminal of said operational amplifier, a first input resistor connected between an output terminal of said second buffer amplifier and the inverting input terminal of said operational amplifier and a second input resistor connected between an output terminal of said third buffer amplifier and the inverting terminal of said operational amplifier.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25719684A JPS61134682A (en) | 1984-12-05 | 1984-12-05 | Element characteristic measuring device |
| JP257196/84 | 1984-12-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1228176A true CA1228176A (en) | 1987-10-13 |
Family
ID=17303010
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000491892A Expired CA1228176A (en) | 1984-12-05 | 1985-09-30 | Electronic device measurement apparatus |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS61134682A (en) |
| CA (1) | CA1228176A (en) |
| DE (1) | DE3542121A1 (en) |
| GB (1) | GB2168162B (en) |
| NL (1) | NL190940C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0721526B2 (en) * | 1987-08-18 | 1995-03-08 | ソニ−・テクトロニクス株式会社 | Element measuring device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2980853A (en) * | 1958-04-28 | 1961-04-18 | Ryan Aeronautical Co | Component output characteristic tracer |
| US3573618A (en) * | 1968-05-27 | 1971-04-06 | William G Dilley | Solid-state characteristic curve tracer attachment for oscilloscopes |
| US4456880A (en) * | 1982-02-04 | 1984-06-26 | Warner Thomas H | I-V Curve tracer employing parametric sampling |
-
1984
- 1984-12-05 JP JP25719684A patent/JPS61134682A/en active Granted
-
1985
- 1985-09-05 NL NL8502440A patent/NL190940C/en not_active IP Right Cessation
- 1985-09-13 GB GB08522687A patent/GB2168162B/en not_active Expired
- 1985-09-30 CA CA000491892A patent/CA1228176A/en not_active Expired
- 1985-11-28 DE DE19853542121 patent/DE3542121A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| GB2168162A (en) | 1986-06-11 |
| GB8522687D0 (en) | 1985-10-16 |
| NL190940B (en) | 1994-06-01 |
| NL190940C (en) | 1994-11-01 |
| NL8502440A (en) | 1986-07-01 |
| GB2168162B (en) | 1988-12-07 |
| JPS61134682A (en) | 1986-06-21 |
| JPH0137701B2 (en) | 1989-08-09 |
| DE3542121C2 (en) | 1991-09-05 |
| DE3542121A1 (en) | 1986-06-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |