Op-Amp as Multivibrator or Oscillator
Category: Operational Amplifier
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
The circuit is designed and simulated in Proteus, can be simulated in any other simulator, like PSIM, NI Multi-SIM or LTspice. The Operational amplifier (Op-amp) is a very versatile electronic device. Lot of different circuits are formed using Op-amp and there are many applications, like signal conditioning, filters, oscillators etc. In this circuit is free running a multivibrator. 1. This circuit uses concept of Schmitt-trigger. Therefore, it is recommended to watch previous circuit of Schmitt-trigger. 2. This free running multi-vibrator has two quasi-stable states i.e., no stable stable such. 3. No external signal is required to change any state. 4. The circuit oscillates between two states and produce a square wave. 5. The component values decide the time of each state, which is called the frequency of oscillation. 6. The calculation for frequency is given below f = 1/2*pi*R2*C1 This circuit oscillates at 100Hz 7. When Vo is at Vsat, the feedback voltage is at upper threshold Vut and is given as Vut = (R3*Vsat)/((R3*(R3+R1)) 8. When Vo is at -Vsat, the feedback voltage is called lower threshold Vlt and is given as Vlt = -(R3*Vsat)/(R3+R1) 9. This configuration of R3 and R1 produces hysteresis and also Schmitt trigger that uses positive feedback. Please share it with your friends, if you like this effort. Thanks