Electronics > Beginners
Bias current sources
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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