A BiCMOS Darlington is shown in Fig. 3.76. The bias voltage V_Bis adjusted for a dc output voltage of 2 V. Calculate the bias currents in both devices and then calculate the small-signal voltage gain Ï…_o/Ï…_iof the circuit. For the MOS transistor, assume W = 10µm, L=1µm, μ_nC_ox= 200 µA / V², V_t= 0.6 V, γ = 0.25 V^1/2, Ï•_f= 0.3 V, and λ = 0. For the bipolar transistor, assume I_S= 10^ˆ’16A, β_F = 100, r_b= 0, and V_A†’ˆž. Use SPICE to check your result. Then add λ = 0.05 V^ˆ’1, r_b= 100, and VA = 20 V and compare the original result to the result with this new transistor data. Finally, use SPICE to compute the dc transfer characteristic of the circuit. 

Fig. 3.76:

Transcribed Image Text:

Vcc = 3 V R = 1 k2 M1 Q2 Vo RB 1 k2 VB