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# Electronics/independant current sources

Question
Hi,

I've solved different circuits using indp. voltage sources and indp. current sources.  I understand that an indp. voltage source could just be a battery with the terminals directly connected to the breadboard.  However, what's an example of an indp. current source?

The only thing I can think of is having a wire connected from a pin output of a microprocessor, for example, Arduino, connected to the breadboard (with a wire connected to ground on the Arduino).  Would this be correct?

There are many ways to think of constant current sources.

The simplest form of an essentially constant current source is a relatively high voltage in series with a very high resistor; especially when the series resistor is very high compared with the load that might be placed at the output.  Think for example of a 1,000 volt dc supply connected to a 1M ohm resistor. If the load were a short the current would be 1000/1M = 1 milliamp.  If the load for this simple circuit were to be only a few ohms, a few hundred ohms or even a few kohms the current would remain pretty much the same, or 1 mamp.  And so forth.

See the following link for a more thorough set of examples:

https://en.wikipedia.org/wiki/Current_source

Hope this helps but let me  know if you need further discussions.

Electronics

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#### ZZ

##### Expertise

Electronics questions about AC, DC and digital theory.

##### Experience

Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

Organizations
IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

Education/Credentials
BSEE University of North Dakota