Question

In a CE transistor amplifier there is a current and voltage gain associated with the circuit. In other words there is a power gain. Considering power a measure of energy, does the circuit voilate conservation of energy?

Answer 1

The different gains in CE transistor amplifier:

1. Ac current gain `beta_(ac) = ((Δi_c)/(Δi_b)) V_(CE)` = constant
2. DC current gain: `beta_(dc) = i_c/i_b`
3. Voltage gain: `A_y = (ΔV_o)/(ΔV_i) = beta_(ac) xx "Resistance gain"`
4. Power gain: = `(ΔP_o)/(ΔP_i) = beta_(ac)^2 xx "Resistance gain"`

The power gain is very high in the CE transistor amplifier. In this circuit, the extra power required for amplified output is obtained from a DC source. Thus, the circuit used does not violate the law of conservation.