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May 2021 StudentZone Quiz Solution


  1. Can you briefly describe two ways in which the gain of the source follower can be improved (closer to one)?


Looking at the gain equation for the source follower circuit:

We can observe that there are to parameters which the gain is dependent on. Therefore, the two alternatives to get a closer to ideal gain (A = 1) are:

  • Decrease the rS value, by increasing ID (not preferable due to the dependance between ID and RL).
  • Increase the value of RL – source load resistor (this can be achieved by adding a current mirror circuit instead of the source load resistance, which provides a constant current ID and a high output resistance, increasing the value of RL)