Question 7.SP.15: Replace the JFET of Fig. 7-5 with the n-channel MOSFET that ......
Replace the JFET of Fig. 7-5 with the n-channel MOSFET that has the parameters of Example 4.4 except V\text{to} = -4 \text{V}. Let R_1 = 200 kΩ, R_2 = 600 kΩ, R_D = R_S = 2 kΩ, R_L = 3 kΩ, C_{C1} = C_{C2} = C_S = 100 μF, and V_{DD} = 15 \text{V}. Assume v_S = 0.250 \sin(2π × 10^4t) \text{V} for computation purposes and determine the voltage gain of this amplifier circuit using SPICE methods.
The netlist code below describes the MOSFET amplifier circuit:
| Prb7_15.CIR vs 1 0 SIN(0V 0.25V 10kHz) VDD 5 0 DC 15V CC1 1 2 100uF CC2 3 6 100uF CS 4 0 100uF R1 2 0 200kohm R2 5 2 600kohm RD 5 3 2kohm RS 4 0 2kohm RL 6 0 3kohm M 3 2 4 4 NMOSG .MODEL NMOSG NMOS (Vto=-4V Kp=0.0008ApVsq + Rd=1ohm Rg=1kohm) .TRAN 1us 0.1ms .PROBE .END |
Execute 〈Prb7_15.CIR〉 and use the Probe and FFT features of PSpice to plot the instantaneous waveforms of v_S and v_L along with their Fourier spectra as shown by Fig. 7-20. The voltage gain follows from ratio of the marked spectra magnitudes with the negative sign accounting for the 180° phase shift observed from inspection of the instantaneous waveforms.
A_{v} = {\frac{v_{L}}{v_{S}}} = -{\frac{0.621}{0.250}} = 2.48
