The correct answer is: A. Limit the maximum emitter current.
The resistance in the emitter circuit of a transistor amplifier is called the emitter resistor. It serves to limit the maximum emitter current, which in turn limits the maximum collector current. This is important because it prevents the transistor from being damaged by excessive current.
The emitter resistor also helps to stabilize the transistor amplifier. This is because it provides a fixed voltage drop across the emitter-base junction, which helps to keep the transistor in a linear operating region.
The emitter resistor also helps to reduce noise in the transistor amplifier. This is because it filters out high-frequency noise signals that would otherwise be amplified by the transistor.
In conclusion, the purpose of resistance in the emitter circuit of a transistor amplifier is to limit the maximum emitter current, stabilize the transistor amplifier, and reduce noise in the transistor amplifier.
Here is a brief explanation of each option:
- Option A: Limit the maximum emitter current. This is the correct answer. The emitter resistor helps to limit the maximum emitter current, which in turn limits the maximum collector current. This is important because it prevents the transistor from being damaged by excessive current.
- Option B: Provide base-emitter bias. The base-emitter bias is provided by the voltage divider formed by the base resistor and the emitter resistor. The emitter resistor does not provide base-emitter bias.
- Option C: Limit the change in emitter current. The emitter resistor does not limit the change in emitter current. The change in emitter current is determined by the change in base current.
- Option D: None of the above. This is not the correct answer. The emitter resistor does serve a purpose in the emitter circuit of a transistor amplifier.