Question

Assuming the operational amplifier in the circuit shown below to be ideal, which of the following properties hold(s) TRUE for the circuit?

• A. It acts as a voltage follower.
• B. It is bistable.
• C. It is astable.
• D. The output voltage is at saturation.

Hint:

- Negative feedback \(\Rightarrow\) linear operation (followers, amplifiers).
- Positive feedback with no input \(\Rightarrow\) saturation/bistable behavior (latches, Schmitt triggers).

Answer 1

The Correct Option is B, D

Step 1: From the figure, the op-amp output is directly fed back to the non-inverting \((+)\) input, while the inverting \((-)\) input is grounded. This is \emph{positive feedback}.
Step 2: With positive feedback and no external input, an ideal op-amp’s output cannot settle at zero; any infinitesimal offset is amplified and drives the output to one of the supply rails (saturation). Therefore the circuit has two stable states (bistable latch), and the output is at saturation (either \(+V_{\!sat}\) or \(-V_{\!sat}\)).
Step 3: It is \emph{not} a voltage follower (which requires negative feedback to the \((-)\) input), and with only wires (no RC timing network) it is not an astable oscillator.