(a) Assuming r5 `, show that the bipolar cascoded mirror of yields Ro > 0y2)ro. Hint: replace the BJTs with their small-signal equivalents, and use the test method, noting that because of the mirror...

(a) Assuming r5 `, show that the bipolar cascoded mirror of yields Ro > 0y2)ro. Hint: replace the BJTs with their small-signal equivalents, and use the test method, noting that because of the mirror action provided by Q3 and Q4, the small-signal current out of Q2’s emitter must mirror that out of Q2’s base. Show also that Ri > 2VTyII . (b) Exploiting the fact that cascoding shifts the point where the extrapolated iO-vO curve intercepts the vO axis from 2VA to 0y2)VA, prove Eq. (4.136).