Use the zero-value time-constant method to estimate the small-signal dominant pole for the current gain of the MOS cascode current mirror of Fig. 4.9. Assume an input ac current source in parallel with I_INand a zero load impedance with V_out= V_GS3+ V_GS4. The bias current I_IN= 100 µA. Compare your answer with the f_Tvalue of the devices. Device parameters are μ_nC_ox= 60 µA/V², γ = 0, λ = 0, V_t= 0.7 V, W = 10 µm, L_eff= 1 µm, C_gs= 20 fF, C_gd= 3 fF, C_sb= C_db= 10 fF at the bias point. Compare your answer with a SPICE simulation of the bandwidth of the circuit and use SPICE to find the bandwidth for I_IN= 50 µA and I_IN= 200 µA.

Fig. 4.9:

Transcribed Image Text:

Vpp IOUT M2 M4 VOUT VIN M1 M3 (a) IOUT Vουτmin Von - VOUT ` M1 active, M2 in triode region Both M, and M2 in triode region (b)