Question

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Briefly explain how do power amplifiers turn a small voltage into a larger voltage?

Answer 1

Let's first understand what a power amplifier actually is. A power amplifier is simply a large signal amplifier used in the output stages of an amplifier. Its purpose is to amplify weak signals to a level so as to drive a certain load at sufficient power. High power in case of power amplifier usually means 1 W or above. Delivery of high power to the load efficiently is usually difficult as the power dissipation in the transistor must be as low as possible.

That's where the power amplifiers come into play as they have high power output stages. A power amplifiers usually harnesses the utility of ac load line as they require larger portion of the load line to amplify weak signals. Depending upon the position of Q points, there are various categories of power amplifiers such as A, B, AB and C. Power amplifiers are supplied with external power supplies in order to achieve this task of large signal amplification. Efficiency is never 100%.