Question B.11: Using PSpice/SPICE to plot the pulse response of a CR circui...

For τ = 0.1 ms, let C = 0.1 µF. Then

R=\frac{\tau}{C}=\frac{0.1 ms }{0.1 \mu F }=1 k \Omega

For τ = 1 ms, let C = 0.1 µF. Then

R=\frac{\tau}{C}=\frac{1 ms }{0.1 \mu F }=10 k \Omega

For τ = 5 ms, let C = 0.1 µF. Then

R=\frac{\tau}{C}=\frac{5 ms }{0.1 \mu F }=50 k \Omega

The series CR circuit for PSpice simulation is shown in Fig. B.27.

The list of the circuit file is as follows.

\begin{aligned}&\text { Example B.11 Pulse Response of Series CR Circuit } \\&\text {.PARAM RVAL=1K } \\&\text {.STEP PARAM RVAL LIST } 1 K \quad 10 K \quad 50 K \\&\text { VS } 1 \quad 0 \quad \text { PULSE (OV } \quad 1 V \quad 0 \quad 1 NS \quad 1 NS \quad 2 MS \quad 4 MS ) \quad ; \quad \text { Pulse input voltage } \\&\text { R } \quad 2 \quad 0 \quad\{ RVAL \} \\&\text { C } 1 \quad 2 \quad 0.1 UF \\&\text {.TRAN } 0.1 MS \quad 4 MS ; \quad \text { Transient analysis } \\&\text {.PROBE } \\&\text {.END }\end{aligned}

The plots of the output voltage v_{ O }(t) for three values of the time constant are shown in Fig. B.28.