A BiCMOS Class AB output stage is shown in Fig. 5.43. Device parameters are β_F(npn) = 80, β_F(pnp) = 20, V_BE(on)= 0.8 V, μ_pC_ox= 26 µA/V², and V_t= ˆ’0.7 V.

(a) Calculate bias currents in all devices for V_o = 0.

(b) Calculate the positive and negative limits of V_o for R_L = 200 Ω. Thus calculate the maximum average power that can be delivered to R_L before clipping occurs.

(c) Use SPICE to check (a) and also to plot the complete dc transfer characteristic of the circuit from V_i to V_o. Also plot the waveforms of I_c1, I_c2, and I_d2 for a sinusoidal output voltage at V_o of 2 V and then 4 V zero-to-peak. In the simulation, assume bipolar parameters as in Fig. 2.32 and MOS parameters as in Table 2.3 (apart from the values of β_F and μ_pC_ox given above).

Figure 5.43:

Fig. 2.32:

+5 V R3 500 RA 100 1 x5 O5 25 O 100 100 A 500 M4 25 RL Va 200 10 K2ER M2 500 02 x25 10 k2 R2 -5 V VIN 81-L Vertical npn Transistor with 2 um Emitter Area Lateral pnp Transistor with 2 m? Parameter Emitter Area Br VA Is Ico BVCEO BVCBO BVEBO 120 50 35 V 30 V 6 x 10-18A 1 pA 6 x 10-18A 1 pA 14 V 18 V 18 V 18 V 10 ps 5 ns 650 ps 5 ns TF TR 400 2 200 2 re 100 2 20 2 rex 40 2 10 2 5 fF 14 fF 0.8 V 0.7 V ne 0.4 0.5 5 fF 15 fF 0.6 V 0.6 V 0.33 0.33 Coo (Cho) 20 fF 40 fF 0.6 V 0.6 V 0.33 0.4 3.