Question

In the circuit shown below, $D_1$ and $D_2$ are silicon diodes with cut-in voltage of 0.7 V. $V_{IN}$ and $V_{OUT}$ are input and output voltages in volts. The transfer characteristic is _____________

Hint:

Always add the diode cut-in voltage (0.7 V for silicon) to any DC bias source in series when determining the clipping level in diode limiter circuits.

Answer 1

Step 1: Circuit description.
The circuit has two diodes $D_1$ and $D_2$ connected in anti-parallel arrangement with respect to the input $V_{IN}$, and both connected to the output node $V_{OUT}$. A $1\,\text{k}\Omega$ resistor is connected from $V_{OUT}$ to a $1\,\text{V}$ DC source.
Step 2: Conduction conditions.
- For $V_{IN}>1.7$ V, $D_1$ conducts (since $V_{IN} - V_{OUT} \geq 0.7$ V). The output clamps accordingly.
- For $V_{IN}<-1.7$ V, $D_2$ conducts, clamping the output in the opposite polarity.
- For $-1.7 \leq V_{IN} \leq +1.7$, both diodes are OFF, and the output follows the linear relationship.
Step 3: Transfer characteristic.
Thus, the $V_{OUT}$ vs. $V_{IN}$ curve is linear within $\pm 1.7$ V and saturates (clamps) outside this range. This corresponds exactly to the graph in (A).
\[ \boxed{(A)} \]