Question

A transistor, when connected in common emitter mode, has a:
A. High input resistance and low output resistance
B. Medium input resistance and high output resistance
C. Very low input resistance and a low output resistance
D. High input resistance and a high output resistance

Answer 1

A common-emitter amplifier (CEA) is one of three fundamental single-stage bipolar-junction-transistor (BJT) amplifier topologies used as a voltage amplifier in electronics. It has a high current gain (usually around 200), a medium input resistance, and a high output resistance. A common emitter amplifier's output signal is ${180^ \circ }$ out of phase with the input signal.

Complete answer:
In amplifier circuits, common emitter circuits are the most common form. Because the current is large, the voltage and power gains are considerable, and the output impedance to input impedance ratio is minimal. CE circuits are well suited for voltage amplification, especially at low frequencies, because they have a large voltage gain and a modest current gain. It's also used to make low-noise and radio-frequency amplifiers.

A voltage amplifier is created by connecting the transistors in a common emitter mode configuration. The output impedance of a voltage amplifier must be low, however in CE mode, the transistor has a high output impedance and a medium input impedance. The difference in phase between input and output.

Therefore, the correct option is B.

Note: When a transistor is utilised as an amplifier in the common emitter mode, the base-emitter junction serves as the input junction, while the collector-emitter junction serves as the output junction. Applying forward voltage to the input junction makes it forward biased, while applying reverse voltage to the output junction makes it reverse biased.