FET Fundamentals Unit 4 – JFET Current Source
UNIT 4 – JFET CURRENT SOURCE
UNIT OBJECTIVE
At the completion of this unit, you will be able to describe the operation of a JFET current source
by using dc measurements.
UNIT FUNDAMENTALS
A constant current source supplies a fixed value of current to a varying load resistance.
This circuit illustrates the constant current source principle.
In this circuit, RA (1 MΩ) is so much larger than RL (0Ω to 500Ω) that the circuit current (IT) is
mainly controlled by RA. Therefore, IT is determined by the equation below.
IT = VA /RAChanges in the load resistor have little or no effect on IT.