In the overload protection circuitry for Q20 consists of R7, Q21, R11, Q24, and Q23. Suppose the op amp is trying to swing vO negative, but because of an overload condition, Q4 steers all of IC8 (519...

In the overload protection circuitry for Q20 consists of R7, Q21, R11, Q24, and Q23. Suppose the op amp is trying to swing vO negative, but because of an overload condition, Q4 steers all of IC8 (519 A) toward the second stage. (a) Assuming Is21 5 Is24 5 Is23 5 2 fA, fi nd the current drawn by Q20 (this is ISC for the current sinking case). Hint: fi nd IC23, Is24, IC21, and fi nally VEB21. (b) What value should R7 be changed to if we want ISC 5 15 mA?