In Fig. P4.91 the differential pair Q1-Q2 is cascoded via the CB pair Q5-Q6, and the active load is a Wilson-type mirror. As we know, both the cascode and the Wilson confi gurations enjoy inherently...

In Fig. P4.91 the differential pair Q1-Q2 is cascoded via the CB pair Q5-Q6, and the active load is a Wilson-type mirror. As we know, both the cascode and the Wilson confi gurations enjoy inherently high output resistance, so we expect a dramatic increase in both Ro and adm. (The function of the 1.4-V source, whose details have been omitted for simplicity, is to bias the Q5-Q6 pair so as to keep Q1 and Q2 in the active region over the entire common-mode input range.) (a) Obtain an expression for adm in terms of the betas and the Early voltages of the BJTs (assume r5 ` for simplicity). Hence, show that if all BJTs have the same beta and Early voltage, then the gain simplifi es as adm 5 0p). (d) If VCC 5 9 V, VBEn 5 VEBp 5 0.7 V, and VCEn(EOS) 5 VECp(EOS) 5 0.3 V, what is the permissible output voltage swing?