PSpice/SPICE diode model and analysis The diode circuit shown in Fig. 4.18 has VS = 10 V, Vm = 50 mV at 1 kHz, RL = 1 kΩ, and VT = 25.8 mV. Assume an emission coefficient of n = 1.84. (a) Use PSpice/SPICE to generate the Q-point and the small-signal parameters and to plot the instantaneous output

Question

PSpice/SPICE diode model and analysis The diode circuit shown in Fig. 4.18 has [latex] V_{ S }=10 V [/latex], [latex] V_{ m }=50 mV ext { at } 1 kHz , R_{ L }=1 k \Omega, ext { and } V_{ T }=25.8 mV [/latex]. Assume an emission coefficient of n = 1.84.

(a) Use PSpice/SPICE to generate the Q-point and the small-signal parameters and to plot the instantaneous output voltage [latex] v_{ O }=v_{ D } [/latex].

(b) Compare the results with those of Example 4.9. Assume model parameters of diode D1N4148:

IS=2.682N CJO=4P M=.3333 VJ=.5 BV=100 IBV=100U TT=11.54N

Accepted Answer

[latex] V_{ S }=10 V , V_{ m }=50 mV , ext { and } R_{ L }=1 k \Omega [/latex].

(a) From Example 4.7, the Q-point values are [latex] V_{ D }=0.7148 V ext { and } I_{ D }=9.284 mA [/latex]. The diode circuit for PSpice simulation is shown in Fig. 4.23. PSpice simulation gives the following biasing point and small-signal parameters:

[latex]\begin{array}{lll} ext { ID } & 9.28 E -03 & I_{ D }=9.28 mA \ ext { VD } & 7.18 E -01 & V_{ D }=718 mV \ ext { REQ } & 5.53 E +00 & r_{ d }=5.53 \Omega \ ext { CAP } & 2.10 E -09 & C_{ j }=2.1 nF\end{array}[/latex]

The PSpice plot of the transient response is shown in Fig. 4.24, which gives [latex] V_{ D }=718.35 mV [/latex] and [latex] v_{ d ( ext { peak })}= v_{ o ( ext { peak })}=600.52 \mu V / 2=300.3 \mu V [/latex]. Thus.

[latex] v_{ d }=300.3 imes 10^{-6} \sin \omega t \quad ext { and } \quad v_{ d ( ext { peak })}=300.3 \mu V [/latex]

(b) Example 4.9 gives [latex] V_{ D }=0.7148 V , I_{ D }=9.284 mA , r_{ d }=5.11 \Omega, v_{ d }=254.2 imes 10^{-6} \sin \omega t [/latex], and [latex] v_{ d ( ext { peak })} = 254.2 \mu V [/latex], which agree closely with the PSpice results.

Question 4.11: PSpice/SPICE diode model and analysis The diode circuit show...

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