Voltage, Current and Power Gain on an Amplifier

Voltage Gain (Δv)

The voltage gain is obtained by dividing the output by the input voltage. Δv = Vout / Vin.
For example: If an amplifier has an input signal of 0.1 Vpp (peak-peak volts) and has an output signal of 10 Vpp, the voltage gain is: Δv = 10 Vpp / 0.1 Vpp = 100.

Current Gain (Δi)

The current gain is obtained by dividing the output by the input current of the amplifier. Δi = Iout / Iin.

For Example: We have an amplifier with a current gain of 500 (Δi = 500) and an input current is of 10 uA. If the load of the amplifier is a 200 ohms resistor. What the load voltage will be?

First, you get the output current: Iout = Δi x Iin = 500 x 10 uA = 5000 uA = 5 mA

Then, the load voltage will be: (using the Ohm’s law)
Vout = 200 x Iout = 200 ohms x 5mA = 1000 mV = 1 volt

Power Gain (Δp)

The power gain is obtained by dividing the power delivered at the output terminals by the power received at the input terminals. Voltage. Δp = Pout / Pin

For example: Using the above example and assuming that at the input of the amplifier we deliver 0.1uW (microwatts). What the power gain will be?

We have the input power, now we will find the output power:
The output power is: Pout = V * I = 1 Volt x 5 mA = 5 mW (milliwatts)

Then, the power gain is: Δp = Pout / Pin = 5 mW / 0.1 uW = 50.000