A variable-gain CMOS amplifier is shown in Fig. 8.52. Note that M₄represents shunt feedback around M₆. Assuming that the bias value of V_iis adjusted so that V_GD6= 0 V dc, calculate bias currents in all devices and the small-signal voltage gain and output resistance for V_cequal to 3 V and then 4 V. Compare your answer with a SPICE simulation and use SPICE to plot out the complete large-signal transfer characteristic of the circuit. Use μ_nC_ox= 60 µA/V², μ_pC_ox= 30 µA/V², V_tn= 0.8 V, V_tp= ˆ’ 0.8 V, λ_n= λ_p= 0, and γ_n= 0.5 V^1/2.

Fig. 8.52:

Transcribed Image Text:

VDp = 5 V 20 M3, 20 20 M2 M5 R1 M4. 10 k2 2 Ve |M6 20 M1 20 Vo