![]() ![]() This causes reduced output voltage in opposite direction. The increased collector current causes a high voltage drop across the collector load resistance (R C).ĭuring the negative half cycle of the input signal, the forward bias across the emitter – base junction is decreased. Hence, from the n – types emitter more electrons flow to the collector through the base. Circuit Diagram of Transistor Amplifierĭuring Positive half cycle of the input signal, the forward bias across emitter – base junction is increased. In this way, a weak signal applied to the input circuit amplified in the output circuit, hence the transistor acts as an amplifier. Since the collector current flowing through a high load resistance RC produces a large voltage across it. Due to transistor action, same change occurs in the collector current. Since the input circuit has low resistance (because of forward biased), hence a small change in signal voltage causes a huge change in emitter current. This DC voltage is known as Bias Voltage and its magnitude is such that it always makes the emitter – base junction forward biased regardless of polarity of signal. For this, a DC voltage VBB is applied in the input circuit in addition to signal. In order to achieve desired amplification, emitter – base junction must remain forward biased. The weak signal is applied between the emitter – base junction and output is taken across the load connected in the collector circuit. A transistor can increase the strength of a weak signal and hence it can be used as an amplifier in a circuit. ![]()
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