Astable multivibrator using op amp negative feedback circuits

  
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Astable multivibrator is an electronic device which can continuously shift between its two states with respect to the output. If the output corresponding to one particular state is high, then the output corresponding to the other state is low. This nature of the circuit is useful in producing continuous output stream of pulses. There is no need fo
Astable multivibrator using op amp negative feedback circuits - schematic

r external triggering in case of astable multivibrator circuits. Simply turn on the power and the circuit start oscillating between its two states. Since it is an oscillator, a positive feedback can be found in this kind of circuits also. It is very easy to realize an astable multivibrator using op-amp ICs. The following circuit is an implementation of astable multivibrator using the 741 op-amp IC. In the above circuit, you can see a positive feedback introduced into the non-inverting pin of the 741 IC, after dividing the output voltage from pin6 using two resistors R1 and R2. There is a capacitor connected to the inverting pin of the op-amp. This capacitor charges through the pot RV1. Initially the capacitor is uncharged condition, and we can expect 0V at the inverting pin of the op-amp. In this condition the output is high, and the non-inverting pin of the op-amp is getting a voltage, which is the output voltage divided by the two resistors. The capacitor starts charging to the high voltage of the output pin through the variable resistor RV1. While it is charging the potential at the inverting pin gradually increases. Eventually at some point of time, the voltage at the inverting pin reaches slightly above the voltage at the non-inverting pin. At this point of time the output of the op-amp goes low (negative) abruptly. When the output pin becomes negative, the capacitor suddenly discharges to zero and then starts charging...



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