Current Sources Page

    Current sources

    Many applications require current sources rather than voltage sources. Current source provides a constant current to the output. This currentdoes not depend on the output voltage. An idea current source is a high output impedance device: it willsupply current, but does not show in other ways on the load circuit.When you need a low-current source, using a linear regulator isa typical approach. When you need a high-current source, using a linear regulator is inadvisable, because of the high power dissipation in the series resistor. To solve the wasted-power problem, you can use a switch-mode regulator. In some applications current signal sources are needed for measurement purposes. One very easy trick is to insert a large value resistor (compared to the impedance of the circuit measured) in series with the generator. This willessentially convert your constant voltage generator to a constantcurrent source. This is not completely ideal current source, butgood enough approximation for most applications, where the load resistance is much smaller than the current limiting resistor resistance.

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