Q. On a CD amplifier Rs = 4k?, µ =50 and r =35k?. Evaluate the voltage gain Av.
Av = Vo/Vi = µRs / (µ+1)Rs + r
= 50×4×10^3 / ((50+1)×4×10^3) + (35×10^3)
= 0.836
The positive value indicates that the voltages Vo and Vi are in phase and further note that Av < 1, for CD amplifier.