AN103
AN103 is The FET Constant-Current Source/Limiter manufactured by Siliconix.
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The FET Constant-Current Source/Limiter
Introduction
The bination of low associated operating voltage and high output impedance makes the FET attractive as a constant-current source. An adjustable-current source (Figure 1) may be built with a FET, a variable resistor, and a small battery. For optimum thermal stability, the FET should be biased near the zero temperature coefficient point.
D S RL RS
- +
A change in supply voltage or a change in load impedance, will change ID by only a small factor because of the low output conductance goss.
DID = (DVDS)(goss)
(3)
The value of goss is an important consideration in the accuracy of a constant-current source...
