SU1133563A2 - Device for measuring complex conductance - Google Patents

Abstract

DEVICE FOR MEASURING COMPLEX CONDUCTIVITY according to ed. St. 987535, characterized in that, in order to increase measurement accuracy, a fourth synchronous detector, a fourth DC amplifier, a second reference voltage source, and a second RC circuit are introduced, the first input of the fourth synchronous detector connected to the output of the second selective amplifier and the second input is connected to the second output of the first high-frequency generator, and the output of the fourth synchronous detector is connected to the first input of the fourth DC amplifier, the second input of which is connected to the second regular enrollment reference voltage, and an output via the second RS -chain coupled to a second input of the output block 5 made controllable.

Description

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The invention relates to instrumentation technology and can be used to automatically measure and control electrical and radio components such as bipolar, as well as to measure the complex conductivity of semiconductor structures (MOS, diodes, Schottky barriers, photodiodes, transistors, etc.) depending from a constant polarizing voltage and an alternating test signal. But the main author, sv. No. 987535. A device containing a high-frequency first generator, connected by a first output to a first input of a control phase shifter, the output of which is connected to the first input of a first balanced mixer, the output of which is connected to an input of the output unit through a low-pass filter, the first output of which is connected to the first terminal of the measured two-terminal, the second terminal of which is connected to the input of the limit switch, the output connected to the input of the first broadband amplifier, the output of which is connected to the first input House second balanced mixer whose output is connected to the input of the first selective amplifier vkodom connected to the first inputs of the first and third synchronous detectors, vkody are connected to inputs of the third and the second DC amplifiers, the outputs of Ko. The first output of the output unit is also connected to the first output of the reference capacitor, the second output of which is connected to the first output of the measuring capacitor, the second output of which is connected to the ground bus, the first output of the measuring capacitor is connected to the input of the second wideband amplifier . whose output is connected to the first input of the third balanced mixer, the output of which is connected to the input of the second selective amplifier, the output connected It is connected to the first input of the second synchronous detector, the output of which is connected to the first input of the first DC amplifier, the second input of which is connected to the first reference voltage source, and the output through the first H5 circuit is connected to the second input of the controlled phase shifter, block constant displacements, the first output of which is connected to the first output of the sample being measured, and the second output is connected to an external voltage recorder, the second output of the output unit is connected to an external frequency recorder and to the input of the frequency converter residual voltage, the output of which is connected to an external recorder, the second output of the first high-frequency generator is connected to the second inputs of the first, second and third synchronous detectors, an automatic control unit whose output is connected to the input of the second (tunable) high-frequency generator, the output of which is connected to the second the input of the first, second and third balanced mixers l. A disadvantage of the known device is the errors due to the non-uniformity of the amplitude-frequency characteristic of the amplifying path. Additional errors in the device are also due to the instability of the amplitude of the tunable high-frequency generator when the frequency changes. The purpose of the invention is to increase the measurement accuracy. The goal is achieved by that a fourth synchronous detector, a fourth DC amplifier, a second reference voltage source, and a second R5 circuit are introduced into the complex conductivity measuring device, the first input of the fourth synchronous detector connected to the output of the second selective amplifier, and the second input connected to the second output of the first high-frequency generator, and the output of the fourth synchronous detector is connected to the first input of the fourth DC amplifier, the second input of which is connected to the second reference source voltage, and the output through the second R5 -circuit is connected to the second input of the output unit, which is controlled. The introduction of new units and their connections allows to completely eliminate errors that occur (not due to the instability of the amplitude of the revised RF generator and output blockade, as well as due to the non-linearity of the amplitude-frequency characteristic of broadband amplifiers and balanced mixers. This allows an increase in the measurement accuracy The drawing shows a block diagram of the device. The device comprises a first high-frequency generator 1, a controlled phase shifter 2, a first balanced mixer 3, a low-pass filter 4, controlled output unit 5, unit 6 constant displacements, automatic control unit 7, second (tunable) high-frequency generator 8 first wideband amplifier 9, second balanced mixer 10, first selective selective amplifier 11, first synchronous detector 12, third amplifier 13 constant current, the third synchronous detector 14, the second amplifier 15 DC, the second broadband amplifier 16, the third balanced mixer 17, the second selective amplifier 18, the second synchronous detector 19, the first amplifier 20 DC, the a new RS circuit 21, a frequency converter 22 is often a voltage, a measurable two-terminal 23, a limit switch 24, a main capacitor 25, a measuring capacitor 26, a first reference voltage source 27, a fourth synchronous detector 28, a fourth DC amplifier 29 the reference source 30, the second R5 circuit 31. The first generator 1 is first connected to the first input of the controlled phase shifter 2, the output of which is connected to the first input of the first balanced mixer 3, the output of which is often connected to the input of the filter 4 t, the output of which is connected to the input of the controlled output unit 5, the first output of which is connected to the first output of the measured two-field 23, the second output of which is connected to the input of the limit switch 24, the output of which is connected to the input of the first broadband amplifier 9 whose output is connected with the first input of the second balanced mixer 10, the output of which is connected to the input of the first selective amplifier 11, the output connected to the first inputs of the first 12 and third 14 synchronous detectors, the outputs of which are connected to the inputs of the corresponding of the third 13.. and the second 15 of the amplifiers 1 34 of the direct current, the outputs of which are connected to external recorders of conductivity and capacitance, respectively; the first output of the output unit 5 is also connected to the first output of the reference capacitor 25, the second output of which is connected to the first output of the measuring capacitor 26, the second output of which is connected to the common bus; The first pin of the measuring capacitor is also connected to the input of the second broadband amplifier 16, the output of which is connected to the first input of the third balanced mixer 17, the output of which is connected to the input of the second selective amplifier 18, the output of which is connected by JC to the first inputs of the second 19 and fourth 28 synchronous detectors, the outputs of which connected; to the first inputs of the first 20 and fourth 29 amplifiers of direct current, to the second inputs of which are connected the outputs of the first 27 and second 30 sources of reference voltage, respectively ; the output of the first DC amplifier 20 through the first RS-circuit 21 is connected to the second input of the controlled phase shifter 2, and the output of the fourth DC amplifier 29 through the second R5-circuit 31 is connected to the second input of the output unit 5. The DC-offset unit 6, the first output of which is connected to the first output of the output unit 5, the second output is connected to an external voltage recorder; The second output of the code block 5 is connected to an external frequency recorder and to the input of the frequency converter 22 is a voltage, the output of which is connected to an external recorder; The second output of the first HF generator 1 is connected to the second inputs of the first 12, second 19, third 24 and fourth 28 synchronous detectors, the input of the second (tunable) RF generator 8 is connected to the output of the automatic control unit 7, and the output is connected to the second inputs of the first 3, second 10 and third 17 balanced mixers. The device works as follows. The RF signal from RF generator 1 with frequency S2 is fed through a controlled phase shifter 2 to the input of a balanced mixer 3, to the second input of which an RF signal is received from a non-tunable RF generator O, the frequency of which can automatically change from Q to about. After mixing in the balanced mixer 3 and passing through the low-pass filter 4, a signal appears at the input of output block 5, the frequency of which is equal to "and can automatically change from S3 Qj - L to 63 g O - - I. Thus, at the output of the output block 5 in A, a voltage Ll & e appears, where IA is the amplitude of the alternating signal, which can i eryte in the output unit 5; (the phase of this signal, which can be adjusted in the controlled phase splitter 2. Next, two structurally identical channels are connected to point A, one of which is directly measuring, and the second is used in the amplitude and phase self-tuning circuits. Thus, the output signal from the output unit 5 is fed to the reference, 1 capacitor 25 (C) with a high quality, while the measuring capacitor 26 () has a voltage, proportional to the current flowing through the capacitor 25 (C) so that the voltage is present at the point B, equal to Jut {(- С „,, A C of the code of the wideband amplifier 16 amplified signal with frequency W О) W g goes to the input of the balanced mixer 17, to the second input which is from the tunable RF- Generator 8 receives a constant amplitude voltage with a frequency from (o to w.) The circuits of these parts are mixed in the balanced mixer 17 and fed to the input of the selective amplifier 18, where the frequency of the frequency P (I Oj-a) occurs, w, -G } j). Thus, at the upstream of the selective amplifier 18, a voltage of 51 frequency equal to int appears (41. kC e: A (j) e, respectively, the amplitude and phase of the input signal of the wideband amplifier 16; the factors A (s) determine amplitude-frequency and phase-frequency characteristics of the amplification and frequency conversion paths. This voltage is fed to the inputs of synchronous detectors 19 and 28, the second inputs of which receive a reference voltage from the RF generator 1 with a frequency of 51. The synchronous detector 19 is tuned to the reactive component of the signal, so on his way out There is a DC voltage proportional to U.ftiul r-smitffl uCpCu. This DC voltage is applied to the DC amplifier 20, where it is compared with the reference voltage from the voltage source 27, and is also amplified through an RS circuit. 21 is supplied to the second input of the controlled phase shifter 2, the closure of the negative feedback loop of the phase locked loop. This connection operates in such a way that the output voltage of the synchronous detector 19 is maintained at zero, i.e. condition Sin (Cf d ((. or (|) d1-vc | (, (1) so that the phase shift in the amplification paths utf (w) when the signal frequency changes is automatically compensated by changing the phase at point A. Synchronous detector 28 is set to the active component of the signal, so that a constant voltage proportional to C06 appears at its output (tfftfKCf (oj) l or, taking into account (1), UftlV) This constant voltage is applied to the DC amplifier 29, where it is compared to the reference voltage from source 30 is amplified and through the RS chain 31 is supplied to the second input of the controlled output A negative amplitude self-tuning circuit of the amplitude. This connection operates in such a way that the output voltage of the synchronous detector 28 is maintained equal to the reference voltage of source 30 with an accuracy better than 1%, U.Hwl -con6t or, that C and C are fixed values, we have 28 UftMu) at the output of the synchronous detector. (2) Gakim, the non-linearity of the amplitude-frequency response of the amplifying and frequency-converting blocks, as well as the instability of the amplitude of the signal from the tunable RF generator 8 automatically compensated The amplitude of the test signal at point A. At the same time, the signal from the output of the output unit 5 is fed to the measured two-port circuit 23, while the measuring capacitor 26 (C, d) is selected depending on the required accuracy and measuring range by switch 24 limits, a voltage proportional to the current flowing through the sample arises, so that the voltage present at the input of the broadband amplifier 9 at point C is equal to (r-G) from the output of the broadband amplifier 9 the amplified signal with frequency g is fed to the input of the balance Mixtures of L 10, a second input of which a tunable RF-generator 8 is supplied a constant voltage amplitude at a frequency of Wj Doso. The signals of these frequencies are mixed in the balanced mixer 10 and fed to the input of the selective amplifier 11, where the frequency separation S () (.) Occurs. Thus, at the output of the selective amplifier 11, a voltage appears with a frequency equal to,) This voltage arrives at synchronous detectors 12 and 14 and further through the amplifiers 13 and 15 of direct current to external recorders. The second inputs of the synchronous detectors 12 and 14 receive the reference voltage from the high frequency generator 1 with the frequency S2. The synchronous detector 12 is tuned to the reactive component of the signal, so that at its output there is a constant voltage equal to U I M Cx4if tfAntfMV d co5ic | tbq) H. The synchronous detector 14 is tuned to the active component of the signal, so that at its output we have a constant voltage equal to:) Cx051HH + LCH1i) - 5 p1CHA + ÑC (C. As the channels containing amplifier 9, mixer 10, amplifier 11 and amplifier 16, mixer 17, amplifier 18, are made identical and, taking into account the fulfillment of conditions (1) and (2), when the frequency of the variable test signal changes, we have at the output of a synchronous detector 12, according to (3), a signal proportional to Q) (/ w , and at the output of the synchronous detector 14, according to (4), the signal is proportional to Cx, which through an amplifier 13 and 15 DC power is supplied to external recording units.From the output of output unit 5, the signal is fed to the input of frequency-voltage converter 22, where the logarithmic frequency conversion O c-Wg to voltage takes place, which is then fed to one of the inputs of the two-coordinate recorder to record the dependences Q ,, / o-EpCSilSu (s). Simultaneously, the output i takes place on a very fine indication of the frequency applied to the sample under study. C. The output of the automatic control unit 7 to the input (tunable RF generator 8 receives a constant or sawtooth voltage for electronically tuning the generator frequency. In the first case, the G / CJ-U and dependences at a fixed frequency are removed, in the second case C x- CO dependencies at a fixed polarizing voltage. From the output of a block of 6 constant displacements on, the bipolar 23, a constant polarizing voltage is supplied, which can also be changed using a ramp to record the corresponding dependences Q, (/, s, or, Odn temporarily at the output U may be connected

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external digital voltmeter for accurate voltage measurement.

In comparison with the known, the proposed device for measuring and recording C-and provides the ability to measure at any frequency in the OjSriOO kHz range, the ability to conduct frequency-dependent measurements in automatic mode with a time of 33356310

Adjustments in frequency from 10 to 300 s with the same measurement accuracy.

The use of the proposed device for research purposes 5 makes it possible to register new processes that, due to their small constant time, cannot be recorded on measuring devices with manual frequency tuning.

Claims (1)

DEVICE FOR MEASURING COMPLEX CONDUCTIVITY lo ed. St. ^: W 987535, characterized in that, in order to increase the accuracy of measurements, a fourth synchronous detector, a fourth DC amplifier, a second reference voltage source and a second RC circuit are introduced into it, the first input of the fourth synchronous detector connected to the output of the second selective amplifier and the second input is connected to the second output of the first high-frequency generator, and the output of the fourth synchronous detector is connected to the first input of the fourth DC amplifier, the second input of which is connected to the second source com of the reference voltage, and the output through the second R5 circuit is connected to the second input of the output unit, made controllable. § £ 00 joint venture> 1133563 2