In the figure, $D1$ is a real silicon $pn$ junction diode with a drop of $0.7V$ under forward bias condition and $D2$ is a Zener diode breakdown voltage of $-6.8V$. The input $V_{in}(t)$ is a periodic square wave of period $T$, whose one period is shown in the figure.
Assuming $10 \tau < < T$, where $\tau$ is the time constant of the circuit, the maximum and minimum values of the output waveform are respectively,
- $7.5 V$ and $-20.5 V$
- $6.1 V$ and $-21.9 V$
- $7.5 V$ and $-21.2 V$
- $6.1 V$ and $-22.6 V$
