# What does this circuit symbol mean? (Circle with horizontal line through it)

I came across the following symbol in a datasheet (functional block diagram on page 8). What does it mean?

For future searchers, the symbol is a circle with a horizontal line (diameter) through it.

Does it just indicate that the current through the branch has a particular value? A current limit? Something else? Thanks.

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## 1 Answer

It's a fixed current source (DIN 40700 style). With an arrow pointing to it an externally controlled current source. In this case it's a CCCS (Current Controlled Current Source), where the generated current is the controlling current divided by 500, resp. 1000, depending on the device.

Other common current source symbols include:

Controlled current sources may be indicated by:

or

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Thanks. I was familiar with the other two symbols, but not this one. I take it DIN 40700 is a German standard of some kind? –  David Aug 22 '12 at 16:43
@David - Yes, "Deutsche Industrie Norm". Most DIN standards have been superseded by European standards ("ENxxxx"). If you look around you'll find more symbols for current sources, but I think these are the most common ones. "The nice thing about standards is that you have so many to choose from." -- Andrew S. Tanenbaum. –  stevenvh Aug 22 '12 at 16:49