Which output signal conditioning element acts as a power amplifier?

• A. Amplifier
• B. Transistor
• C. Saturation
• D. PWM (Pump and Heater)

Answer: (B)

Amplification of the output signal to drive a load is the function of the amplifier stage. It takes a small signal from previous stages and increases its amplitude (voltage, current, or both) so the load receives enough power. A transistor is a device that can realize this function, but on its own it isn’t a complete power amplifier; it needs to be used in a proper biased amplifier circuit to provide the necessary gain. Saturation is the limit where the device can’t increase output any further, which causes distortion and is avoided in linear signal conditioning. PWM (Pulse Width Modulation) is a switching technique to regulate average power, not a continuous, linear power amplifier. So the element that performs the power amplification role is the amplifier.