March 2021 StudentZone Quiz Solution

Questions:

  1. What affects the regulated output voltage as a load to ground is applied to the output voltage of the Band-gap shunt regulator?

Answers:

A practical method to answer to this question is to simulate the circuit using LTspice.

Consider the band-gap shunt regulator circuits below:

R4 was added as load to the output of the circuit, and a list on 3 values (1k, 10kΩ, 100kΩ) were used as steps for the simulation.

The output voltage vs. input current plot is presented in the figure below:

Where the green trace corresponds to R4 = 1k, blue trace R4 = 10kΩ and red trace R4=100kΩ.

We can notice based on this analysis that the input current range for which the output voltage is constant changes based on the value of the connected load. (lower load resistance -> lower input current range).