![]() When v in is positive, v out = – V z1 and when v in is negative v out = + V z 2. The differential input voltage is given as v in = v c – β v out Combination of IL and C acting as a low-pass R-C circuit is used to integrate the output voltage v out and the capacitor voltage v c is applied to the inverting input terminal in place of external signal. A fraction of the output is fedback to the non-inverting (+) input terminal. In the op-amp square-wave generator circuit given in figure, the output voltage v out is shunted to ground by two Zener diodes Z 1 and Z 2 connected back-to-back and is limited to either V Z 2 or –V Z 1. Second, the use of positive feedback gives the circuit hysteresis. First, the high gain causes the op-amp’s output to switch very quickly from one state to another and vice-versa. ![]() In a comparator circuit this offer two advantages. ![]() The comparator uses positive feedback that increases the gain of the amplifier. ![]() The “heart” of the oscillator is an inverting op-amp comparator Like the UJT relaxation oscillator, the circuit’s frequency of oscillation is dependent on the charge and discharge of a capacitor C through feedback resistor R. In general, square waves are relatively easy to produce. The op-amp relaxation oscillator shown in figure is a square wave generator. ![]() The non-sinusoidal waveform generators are also called relaxation oscillators. ![]()
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