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low current to charge cupacitor

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barbar

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current mirroring pico amp


Do someone know a circuit to charge a cup. in very low current (about some nano amp) with good accurate
 

current mirror very low current

The best way is to use a current mirror: It's made like an ECL port with the base of one transistor shorted with it's collector and a load on the collector of the other (Try to make a search for current mirror circuit). By acting on some parameters of this scheme you can make a certain current and duplicate it (even a fraction of it) with a very good accurancy. This is used into DAC IC to stabilize their performances against ageing and temp. drift.
Bye Mrm
 

Thanks for the answard.
Do you know a link where I can find drews of it?
 

Using CMOS current mirror can also achieve such accuracy. At least a current output unit of a few pico Ampere is possible, whereby the MOSFET operates probably in the sub-threshold regime.
 

Try "the art o f e lectroni cs" into the E book forum....There are lots of schemes
 

You could also use a simple current regulator . Just moniter the charge with a galvanometer . Use a high resistance feed resistor.

Barrbear
 

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