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Bias current sources

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aheid:
The attached schematic was pulled from an opamp datasheet. It shows a few bias current sources and sinks.

If I were to implement the circuit as shown, how could I implement those current sources and sinks? Not that I am going to implement the circuit, I'm just curious how this is done in practice.

I've read about the Widlar current source and Wilson current source, would either be a viable option? If so, for a sink, would I switch the NPNs for PNPs and swap the rails or?

aheid:
Aaand I forgot to add the image of course  |O

Wimberleytech:

--- Quote from: aheid on January 02, 2019, 10:13:23 pm ---The attached schematic was pulled from an opamp datasheet. It shows a few bias current sources and sinks.

If I were to implement the circuit as shown, how could I implement those current sources and sinks? Not that I am going to implement the circuit, I'm just curious how this is done in practice.

I've read about the Widlar current source and Wilson current source, would either be a viable option? If so, for a sink, would I switch the NPNs for PNPs and swap the rails or?

--- End quote ---

Short answer: Yes, either could be used.  Which,...depends on a number of things...many outlined in the wiki article.

For a current sourced from Vcc, use PNP.  For current sunk to ground, use NPN.

aheid:
Excellent, thanks!

exe:
I like jfet current sources due to their simplicity. Just a jfet and a resistor.

The catch is for each jfet the resistor has to be selected individually.

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