# Electronic – this electronic symbol labelled “Current Source”

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What is this electronic symbol? How do I physically implement this? simulate this circuit – Schematic created using CircuitLab

When dealing with circuit schematics, an arrow inside a source means that it's a current source, as opposed to a voltage source. The diamond shape means that this is a controlled source. Since the gain makes no mention of amps/volt, this is a current-controlled current source. The gain is one, so this is actually a unity-gain current-controlled current source. An example of a device like this would be a current mirror, where current running through one leg of a device causes an equal current to run through another leg of the device. An advantage of this device is that it acts as a buffer, preventing the output circuit from loading the input.

From wikipedia (http://en.wikipedia.org/wiki/Current_mirror) simulate this circuit – Schematic created using CircuitLab

Basically, the current mirror shown here acts as a current to voltage, then voltage to current convertor. Current flowing into Q1 is converted to a voltage at the base terminal. This voltage then determines the current flowing through the base of Q2, which sets the current flowing through the collector of Q2. It's a fairly common circuit, and you should be able to find it in any undergraduate level electronics textbook, as well as any decent resource online. Other implementations exist, and a search online will probably turn up many circuits you can use.

Edit: Resistor values, transistor part numbers, and voltages are just the defaults in the schematic capture program StackExchange uses. You'll need to do a little math to get a circuit that will work right for you. Note that the above circuit is a very basic circuit, like you would find in a textbook. More practical circuits definitely exist.