Which basic Op-amp regulator allows to increase the emitter voltage?

Which basic Op-amp regulator allows to increase the emitter voltage until the value of inverting input voltage becomes equal to Zener voltage especially when increased voltage is applied to the base of transistor?

Options:

a. Op-amp Series Regulators
b. Op-amp Shunt Regulator
c. Both
d. None

Correct Answer: a. Op-amp Series Regulators

Explanation

As per the configurational arrangement, due to decrease in input voltage or load current, output voltage also tend to decrease.

Thus, it is essential to apply the proportional voltage decrease to an inverting output of Op-amp using potentiometer.

As another op-amp input is under the hold of Zener voltage at a fixed reference value, it gives rise to a small difference voltage across the two inputs of op-amp.

This difference voltage is also known as error voltage and it is amplified due to which the output voltage increases.

Increased output voltage is further applied to the base of transistor by rising the value of emitter voltage till the inverting input voltage becomes equal to reference or Zener voltage.

This action eventually offsets attempted decrease in output voltage by maintaining it at certain value.