Measuring the Sensitivity of an Amplifier (INS036E)

Audio amplifiers do not always bring information about their input sensitivity, i.e., how much signal we need to apply to the input for maximum output power. Here's how we can measure this sensitivity using common instruments:

a) Audio generator or function generator (sinusoidal)

b) Audio Voltmeter or Multimeter (Analog)

c) Charge resistor with output impedance value and dissipation according to the amplifier.



In the figure below we show how to connect the various elements of the circuit.






We initially set the signal generator to produce a signal between 500 Hz and 1 000 Hz sinusoidal. The volume of the amplifier must be all open and the signal output of the generator all closed.

Then slowly open the intensity control of the signal generator to the point where saturation occurs, i.e., the instrument needle stops rising.

At this point we have in the signal generator the intensity of the output signal given by the settings, that is, how many millivolts of signal is being applied to the amplifier. This is the sensitivity of the amplifier.