Why Transistor Amplify Current?

During the negative alternation of the input signal, the transistor current increases because the input voltage aids the forward bias. The output for the negative alternation of the input is a positive alternation of voltage that is larger than the input but has the same sine wave characteristics.

Why does a transistor amplify?

A transistor acts as an amplifier by raising the strength of a weak signal. The DC bias voltage applied to the emitter base junction, makes it remain in forward biased condition. ... Thus a small input voltage results in a large output voltage, which shows that the transistor works as an amplifier.

How transistor is used as current amplifier?

The transistor acts as a switch when a small base current turns on a much larger collector-emitter current. For example, an audio amplifier has two stages of amplification. In the first step, which is called the preamplifier step, the input voltage is amplified, and in the second stage the current is amplified.