The gain of a bipolar transistor drops at high frequencies.

Home » Physical Electronics Devices and ICs » Physical electronics devices and ics miscellaneous » Question

The gain of a bipolar transistor drops at high frequencies. This is because of the—

1. Coupling and bypass capacitors
2. Early effect
3. Inter-electrode transistor capacitances
4. Coupling and bypass capacitors, and interelectrode transistor capacitances

Correct Option: C

The gain of a bipolar transistor drops at high frequencies because of the inter-electrode capacitances. As we know that at high frequency range, the reactance of C_C becomes quite small, therefore it behaves like a short circuit. As a result of this, the loading effect of next stage increases, which reduces the voltage gain. In addition to this, the capacitance of the emitter diode plays an important role at high frequencies. It increases the base current of the transistor due to which the current gain (β) reduces. Hence the voltage gain rolls at high frequencies.