RU1838874C - Rc generator of sinusoidal signals - Google Patents

Abstract

Usage: radio engineering, measuring equipment. SUMMARY OF THE INVENTION: An RC sinusoidal signal generator comprises a controlled positive feedback circuit, a wideband differential amplifier, a phasing circuit, a signal level converter, two control switches, a strobe detector, a peak detector, a limit amplifier, two voltage resistive combiners, an integrator , two sources of reference voltage and an AC / DC converter and have high speed while reducing the unevenness of the level of the exhaust voltage Wives in the frequency range. 1 ill.

Description

The invention relates to radio engineering and measurement technology and can be used in measuring generators of low-frequency signals.

The purpose of the invention is to increase the speed and reduce the unevenness of the output voltage level in the frequency range.

The drawing shows a structural electrical circuit of the proposed RC-re-generator of sinusoidal signals. It contains a controlled positive feedback circuit 1, a wideband differential amplifier 2, a phasing circuit 3, a signal level converter 4, an input controlled second switch 5, a gate detector b, a peak detector 7, an input controlled first switch 8, an amplifier-limiter 9, a first resistive voltage adder 10, an integrator 11, a first reference voltage source 12, a second reference voltage source 13, a second resistive voltage adder 14, a converter

15 AC dc voltage. The signal level converter 4 is made on an operational amplifier 16 (op-amp) and first and second resistors 17 and 18 (R1 and R2).

In the drawing, the following notation is accepted: 11D is the output voltage of the detector; Don per - adjustable reference voltage; 11out - the output voltage of the generator,

The RC-generator of sinusoidal signals operates as follows.

The oscillator unit consists of an oscillating link, consisting of a broadband differential amplifier 2, a phasing circuit 3 (RC circuit of a T-type), included in a negative feedback circuit (OS), a controlled positive feedback circuit 1. Circuit 3 is made in the form of a set of resistors and capacitors with the exact values of the resistances and capacitances. Oscillations occur in the oscillating link when exposed to amplitude control signals (through chain 1), which change the coefficient

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transmission of the circuit of the positive OS, and when exposed to frequency control signals, the level of which is determined by the values of the resistances and capacitances of the RC elements of the phasing circuit 3. High accuracy of the installation and stability of the amplitude of the output sinusoidal signal are achieved thanks to the automatic amplitude stabilization (ASA) system, which includes signal level converter 4, introduced controlled first and second switches 8 and 5, a gating detector 6, a peak detector 7, an amplifier-limiter 9, the first resistive a voltage adder 10, an integrator 11, a first reference voltage source 12, a second reference voltage source 13, a second resistive voltage adder 14, an AC / DC converter 15.

The use of an integrator 11, a source 13, an adder 14 and a converter 15 significantly increases the stabilization coefficient of the ACA system and, as a result, improves the frequency response of the RC generator compared to the prototype.

Under the conditions of self-excitation, the alternating voltage from the output of the amplifier 2 is supplied to the converter 15, where it is converted to a direct current voltage. The output voltage of the converter 15, containing both a constant and a variable component, is compared in the adder 14 with the reference voltage of the source 13 and with the output alternating voltage of the amplifier 2. As a result, the voltage difference containing the residual value is input to the integrator 11 a variable component, additionally filtered by the integrator 11. The output voltage of the latter is compared in the adder 10 with the reference voltage of the source 12 and with the output voltage of the amplifier 2. The difference signal from the output of the sum RA 10 is fed to the input of amplifier-limiter 9, the output signal of which is in the form of cut off vertices of the sinusoid that goes to the input of detector 6 when the RC generator is operating at the beginning of the low frequency range (for example, 5 Hz-5 kHz) or to the input of detector 7 when RC generator in the remaining low frequency range (for example, 5-500 kHz),

The use of a gating detector at the beginning of the low frequency range can significantly reduce the settling time of oscillations, i.e. increase performance. This is due to the significantly lower inertia of the gating detector compared to the peak. In the remaining low frequency range, a peak detector is simpler and more efficient. The gate detector 6 is controlled by two signals - from the first and from

the second outputs of the phasing circuit 3. Switching the output of the amplifier-limiter 9 and the input of the converter 4 are carried out simultaneously by the first switch 8 and the second switch, respectively

about. The output signal PD of the used detector (6 or 7) goes to the input of the converter 4, where both its level and polarity change. The input signal 11e of the converter 4 goes to the non-inverting input of the operational amplifier 16, to the inverting input of which an adjustable reference voltage Don per is supplied through the resistor R2. The resistor R1 is included in the negative OS circuit of the amplifier 16. Due to the chosen construction of the converter 4, the input signal level Au can vary from units of volts to fractions of a volt, which directly affects the amplitude of the residual sawtooth voltage in

signal 1) d. Lowering the UA to 0.3 ... 0.5 V significantly reduces the amplitude of the residual sawtooth voltage at 11d. And this, in turn, significantly increases the rate of restoration of oscillations during frequency switching and reduces the harmonic coefficient Kg of the output sinusoidal signal.

The mechanism for reducing Kg is as follows. The resistance of the channel of the field-effect transistor used as a circuit 1 of the controlled positive OS depends on the level of the control signal supplied to its input from the output of the converter 4. If this signal contains a residual sawtooth voltage of a large level, then during this period the voltage will be large and a change in the resistance of the drain-source channel of the field effect transistor, which typically fixes circuit 1, and a change in the depth of the positive OS. As a result, the harmonic coefficient Kg of the output signal will also be large. To decrease Kg, it is necessary to increase the time constant

a detector (6 or 7), which reduces the amplitude of the residual sawtooth voltage. But this leads to a decrease in the speed of the generator. Therefore, choosing from the point of view of the required speed the detector time constant, it is necessary to reduce the value of Kg by lowering the signal level id. So, if id is “-4 V, then the amplitude of the sawtooth voltage in it is 20-25 mV, and Kr is 0.015%. If the same voltage is 0, Z.

ZmV.a Kg-0.002%.

At the same time, there must be a high level signal (e.g. +1.5 V) at the control input of circuit 1. Thus, the converter 4 provides a high level signal at the input of the converter 4 at a low signal level id, which is achieved by the voltage Don per.

The new construction of the proposed generator and the use of new blocks and elements in it in a certain inclusion made it possible to significantly increase the speed of the generator at the beginning of the low frequency range and reduce the unevenness of the output signal level in the entire frequency range .: In addition to the fact that it was possible to reduce the coefficient by an average of harmonics of the output signal. (At the same time, consumers of the proposed generator do not need to use (together with the generator) an expensive high-precision electronic voltmeter operating in a wide frequency range.

Claims (1)

The claims An RC sinusoidal signal generator containing a wideband differential amplifiers, a controlled positive feedback circuit that is connected between the output and a non-inverting input of a wideband differential amplifier, between the output and the inverting input of which a phasing circuit, a peak detector, a limiting amplifier, the first source are connected reference voltage, the first resistive voltage adder, the first vt second inputs of which are connected respectively to the output of the first reference voltage source tim and output broadband differential amplifier, which is also an output of the HC generator of sinusoidal signals, wherein the input of the phasing circuit is connected to the output of the broadband differential amplifier, to whose inverting input the first output of the phasing circuit is connected, and the output of the first resistive voltage combiner is connected to the input of the amplifier-limiter, distinguishing -5 so that, in order to increase the speed and reduce the unevenness of the output voltage level in the frequency range, a signal level converter, a gating detector, is introduced sequentially 10 connected DC-DC converter, a second resistive voltage adder and an integrator, the output of which is connected to the third input of the first resistive voltage adder 15, the signal level converter is made on an operational amplifier and series-connected first and second resistors, while the first resistor is connected between the output and the inverting input of the operational amplifier, the other output of the second resistor is an input of the adjustable reference voltage of the level converter signal output connected limiting amplifier 5 with the inputs of the gating detector and the peak detector through the input controlled first switch, the outputs of the gating detector and the peak detector are connected to the non-inverting input of the operational amplifier through the input controlled second switch, the output of the operational amplifier is connected to the control input of the controlled positive feedback circuit 5 zi, first and second control inputs a gating detector connected respectively to the first and second outputs phasing circuit, broadband output differential amplifier connected 0 also with the input of the AC voltage converter to a constant and with the second input of the second resistive voltage combiner, the third input of which is connected to the output of the second reference voltage source5.