An amplifier has an input resistance of 600 ohms and a resistive load of 75 ohms. When it has an rms input voltage of 100 mV, the rms output current is 20mA. Find the gain in dB.
Input power is P = (100 x 10) /600 W = 16.7 W
Output Power is P = (20 x 10) x 75 W = 30 m W
Gain is P/P = (30 x 10)/(16.67 x 10)
10 log 1.8 +10 log = 2.6 + 30 = 32.6 dB.