SU1257817A1 - Generator of trapezoidal voltage - Google Patents

Abstract

The invention relates to a pulse technique. It can be used, for example, in measuring devices. The purpose of the invention — extending functionality at the same time as increasing reliability — is achieved by ensuring the formation of trapezoidal voltage with stable levels of peaks and pauses of long duration and with adjustable time intervals. The goal is achieved by introducing adjustable double-sided stops 3 and 4 into the device. In addition, the drawing shows an operational amplifier 1, which forms an integrator with a resistor 5 and a capacitor 2, operational amplifiers 6 and 7, pulsed diodes 8 and 9, voltage follower 10. The instability of the levels of the tops and pauses of the trapezoidal pulses determines with zero zero operational amplifiers with a drift and does not exceed units of millivolts. 2 W1, (L ts9 CD 00 and Out.

Description

i 1

The invention relates to a pulse technique and can be used, for example, in measuring devices.

The purpose of the invention is to enhance the functionality by ensuring the formation of trapezoidal voltage with stable levels of vertices and pauses of long duration and with adjustable time intervals with simultaneous increase in reliability of operation.

Figure 1 shows the structural electrical circuit of the device; FIG. 2 shows diagrams for his work.

The device contains an operational amplifier 15 whose input is connected to the first capacitor plate 2, the first and second adjustable double-sided stops 3 and 4, the first of which is connected between the device input bus and the input of the operational amplifier 1, the second between its output and the second capacitor plate 2,

In Figure 2, the following definitions are accepted: V is the input voltage of the imager; V - voltage on

fobiXi

- for example, the input of amplifier 1; V is the output of the amplifier I; output voltage at the shaper output; + V × voltage sources of the reference voltage of the limiter 3; + V, - V - output voltages

N o, I, Q with

the amplifier 1, which is in the saturation mode I V,, Vg is the voltage of the sources of the reference voltage of the limiter 4; t, is the instant of time when the input voltage changes its polarity; j tj is the instant of the beginning of the formation of the rear front of the output voltage; tj is the moment when the output voltage reaches the limiting level V; t is the moment when the voltage at the input of the amplifier 1 is of level V.

The operational amplifier 1, having a large input resistance, together with a resistor 5 and a capacitor 2 forms an integrator which is intended to form linearly varying sections of the output voltage. As an operational amplifier 1, for example, a K140UD8A or K544UD1 chip can be used.

The first two-sided limiter 3 is designed to limit amp578172

The voltages at the input of amplifier 1 are up to levels of + V, -VQ, which accelerates the output of amplifier i from saturation when the polarity of the input signal changes.

5G e, Limiter 3 may contain operational amplifiers 6 and 7, limiting resistor 5, pulsed diodes 8 and 9, reference voltage source, -V (not shown). The 10 rotating inputs of amplifiers 6 and 7 are connected to the output of the limiter 3, to the anode of diode 8 and the cathode of diode 9, respectively. The outputs of the amplifiers 6 and 7 are connected to the cathode of the diode 8

15 and the anode of diode 9, respectively. The non-inverting inputs of amplifiers 6 and 7 are connected respectively to the sources of the reference voltage + Vg and -V ,,. Amplifiers 6 and 7 can be implemented 20 on the K140UD8A or K544UD1 integrated circuits. As diodes 8 and 9 you can use diodes KD503A.

The second two-sided limiter 4 is constructed in a similar pattern and 25 additionally has a voltage follower 10 at the output intended for —generating the output impedance. The limiter 4 limits the output voltage 30 of the former at a given upper or lower level.

The device works as follows.

35

Rectangular square-wave pulses with amplitude V are received at the input of the former (Fig.), Two to three times greater than the voltage of the non-source id. Suppose that negative voltage -Vgx is applied to the input of the former (Fig. 2a). Due to the current through the output impedance of the amplifier 7, the diode 9 and the resistor 5, the output of the first limiter 3 maintains the voltage of the reference source -V, which provides the saturation mode with the output voltage + V of amplifier 1 (Fig. 2). This voltage is limited by the second limiter 4 to the voltage level of the reference source.

50 Vg and goes to the output of the shaper. Thus, on the first plate of the capacitor 2, the potential -V is maintained, on the second plate -Vg and at the output of the former, the upper level of the trapezoidal pulse V is formed (Fig. 2d).

At time t, the input voltage changes its polarity. Capacitor

2 begins to recharge through the input voltage source, resistor 5 and output resistance of limiter 4. At time t, when the voltage at the input of amplifier 1 approaches s to zero, amplifier 1 goes out of saturation. After this, the second limiter 4 goes into the pass mode and closes the negative feedback circuit of amplifier 1 (Fig. 26). Starting to recharge capacitor 2 with a constant current I

Yi l

R

provided.

that the resistance R of the resistor 5 is much less than the input resistance of the amplifier 1. At the output of the device, the trailing edge of the trapezoidal pulse begins to form. The time interval between the moments of changing the polarity of the input voltage and the beginning of the formation of the rear front of the output voltage

t - t t End +

Vp-) V

Bx

25

where t is the integrator time constant;

R is the resistance of the resistor 5; C - capacitor capacitance 2;

At time t.

the shaper of the imager reaches level V, limiter 4 goes into the limiting mode and breaks the negative feedback circuit of amplifier 1. At the output of the device, the formation of the lower level of the trapezoidal pulse begins. The potential on the second plate of the capacitor 2 is equal to V, and on the first increases from zero to the positive region due to further recharging of the capacitor 2 from the input source. With increasing potential at the input, amplifier 1 goes into saturation mode.

At time t, when the voltage at the input of amplifier 1 reaches + V, the diode 8 of limiter 3 is released and then the level of + V is maintained by means of limiter 3 until the polarity of the input pulse is measured. The time at which the potential at the input of amplifier 1 increases from O to + V,

- t.

 R-c (v:

Vex

- V

at

change em

ex

tj moment is polarity and

processes similar to those that have been repeated since time t are repeated, with the difference that the voltages change in opposite directions. Thus, a trapezoidal voltage is formed at the output of the former.

The shaper allows one to achieve the required effect with small instrumental costs — to obtain trapezoidal voltage with stable levels of vertices and pauses of long duration and with adjustable time parameters. Instability

The 15 levels of the vertexes and pauses of the trapezoidal pulses are determined only by the zero drift of operational amplifiers. and for these operational amplifiers does not exceed millivolts.

The time parameters (the duration of the vertex and the pause between pulses) are adjusted when the circuit is supplemented with appropriate feedback circuits (1) and becomes possible due to the stable temporal position of the output pulses relative to the input ones. The temporal position of the output pulses is stabilized by reducing the time delay between the moments of change in the polarity of the input pulse and the moments of the beginning of the formation of fronts and decays of the output pulse of trapezoidal voltage. So, with V 35 100 U, tj-t,, 0n: from formula (1) and (2); Atti moments almost coincide.

Claims (1)

Invention Formula 40 A trapezoidal voltage shaper comprising an operational amplifier, the input of which is connected to the first capacitor plate, characterized in that I5 in order to extend the functionality by ensuring the formation of trapezoidal voltage with stable levels of vertices and pauses of long duration and with adjustable SO time intervals with a simultaneous increase in the reliability of its operation, the first J and the second adjustable bilateral are introduced into it limiters, the first of which is included-), (2) 55 chen between the device input bus and the input of the operational amplifier, the second pulse - between its output and the second circuit capacitor plate. when the output is 30