Exercise 3.9 Biasing an amplifier with an NPN


An answer:

IC = βfe βfe + 1IE IE = V E R4 V E = V DD IBR1 V BE IB = IC βfe

back substitution and separation of variables yield

IC = βfe βfe + 1 V DD IC βfeR1 V BE R4 = βfe βfe + 1 V DD V BE R4 + R1 βfe+1