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This is what a non-ideal amplifier looks like. The horizontal resistors represent the intrinsic resistance of the voltage sources(left: Rs(source), right: Ro(out)). The left vertical resistor determines the input voltage(normally called Ri), and the right resistor represents the load(RL). The gain of the controlled source is NOT the gain of the amplifier, because this amplifier is not ideal.
An Ideal amplifier looks like this:
Ro = 0(Short circuit)
Ri = ∞(Open circuit)
Calculate the gain with:
Po/Pi
Vi = Vs * Ri/(Ri+Rs)
Vo = Av * Vi * RL/(RL + Ro)
Po/Pi = (Vo²/RL)/(Vi²/Ri) = G
Gain in Decibels: 10 * log(Po/Pi)
THIS EXAMPLE:
Vi = 1.8, Vo = 6.75
Voltage gain = Vo/Vi = 3.75
G = Po/Pi = 21.1 OR 13,2 dB
If this amplifier would be ideal, the gain would equal the gain of the controlled source(try out the formula and see for yourself).
Note: Po is Vo²/RL! Vo² is divided by the LOAD resistor, and NOT the intrisic resistance of the controlled source!
Av = Controlled source's gain
Vs = Source voltage
Comments are welcome
