(a)Figure 6.60a shows a folded version of the op amp in Fig. 6.15. A differential inter stage level-shifting network composed of voltage sources V 

has been inserted between the first and second stages. Assume that current source I₁is implemented using an n-channel transistor with overdrive of V_ovn, which is equal to the overdrives of the other n-channel transistors shown in Fig. 6.60a. Assume that current sources I₂ and I₃ are each implemented using one p-channel transistor with an overdrive of V_ovp. In the resulting op amp, only n-channel transistors conduct time varying currents. Find the input common-mode range and the maximum output swing of the op-amp in terms of V_DD, ˆ’V_SS, the level-shift voltage V, the threshold voltages of individual transistors, and the overdrives V_ovn and V_ovp.

(b) Figure 6.60b shows a realization of an active floating level shift (active battery). Design this level-shift circuit to give a battery voltage of 1.5 V with a small-signal resistance less than 1 k„¦ at I = 100 μA dc. Ignore the body effect. Use I_B=100 μA and V_DD = V_SS =1.65 V. Use SPICE to plot the large-signal Iˆ’V characteristic for V = 0 to 1.65 V. Use μ_nC_ox =194 μA/V², λ = 0, and V_t = 0.6V. For SPICE simulations, connect the lower end of the battery to the negative supply.

Figure 6.60b

Figure 6.15

Transcribed Image Text:

VDD 13 13 I4 14 Cc -Vss (a) VDD M1 M2 1в -Vss (Б)