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Simple Current Source (shortened). Click to view full-size picture.

What is the idea behind this circuit?

Simple Current Source (shortened)

Idea: Converting voltage into current by using resistance.

The combination of a voltage source and a voltage-to-current converter acts as a simple current source.

Actually, there are not constant current sources in the nature; so, we have to build them. According to the general idea above, we connect a voltage-to-current converter after the voltage source. If we use a current load with zero resistance, the combination will act as a constant current source.

Implementation: Using a resistor as a voltage-to-current converter.

The simple current source sonsists of a voltage source and a humble resistor connected in series. If the output is shortened, a constant current will flow through the circuit. Click to view full-size picture.

We see this idea in the circuit of the simplest current source. Here the humble resistor R is connected in series with the voltage source V. The circuit output is shortened with an ideal current load (just a piece of wire). As a result, a constant current I = V/Ri flows through the circuit.

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