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Need a 100uA sourcing and sinking current source circuit

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leongch

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hi, i need a 100uA sourcing and sinking current source circuit with output clamped to 5V. Any1 can help me out? For 100uA sourcing current circuit, i already found the solution using the LM334. But I would like to clamped its output voltage to 5V, anyone can help me to do so?

I need the sinking current source circuit badly.

Spec of the circuits
100uA sourcing current source with output clamped to 5V
-100uA sinking current source with output clamped to 5V
the error of this sinking n sourcing current source must be less than 5%
 

IanP

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In both cases (sinking and sourcing) you can try circuit suggested by VVV at:
Bear in mind, that TL431 is 2.5V voltage reference, so to generate 100µA of current you will need R1 to be --> 2.5V/100µA = 25kΩ ..

As simple voltage clamping device use 5.1V zener diode or another TL431 shunt regulator with two external resistor to adjust the clamping vltage to 5V ..

So, for sourcing current, use the same circuit with P-channel mosfet (or PNP BJT), whereas for sinking current build a mirror-circuit reversing "everything" upside-down and use N-channel MOSFET (or NPN BJT) ..

Regards,
IanP
 

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