Clipper circuit in OpAmp
If the value of the input voltage Vi is less than the value of the reference voltage Vref, then the diode D1 conducts. Then, the circuit given above behaves as a voltage follower. Therefore, the output voltage V0 of the above circuit will be same as that of the input voltage Vi, for Vi &lt; Vref

If the value of the input voltage Vi is greater than the value of reference voltage Vref, then the diode D1 will be off. Now, the op-amp operates in an open loop since the feedback path was open. Therefore, the output voltage V0 of the above circuit will be equal to the value of the reference voltage Vref, for Vi > Vref