CBSE Class 12-science Answered

The Transistor as an Amplifier

– Amplification is the process of linearly increasing the amplitude of an electrical signal.

– A transistor can act as an amplifier directly using the gain, b.

– Keep in mind that when a transistor is biased in the active (linear) region, the BE junction has a low resistance due to forward bias and the BC junction has a high resistance due to reverse bias.

i) DC and AC quantities

– Amplifier circuits have both ac and dc quantities.

– Capital letters are used will be used for both ac and dc currents.

– Subscript will be capital for dc quantities.

– Subscript will be lowercase for ac quantities.

ii) Transistor amplification

– A transistor amplifies current because the collector current is equal to the base current multiplied by the current gain, b.

– Base current (I_B) is small compared to I_C and I_E.

– Thus, I_C is almost equal to I_E.