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current source that independent of power supply

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surianova

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hi all!

do u all have any reference about current source that independent of power supply?

for example, i want to get reference current 5 uA, it won't chnage across power supply from 3 to 3.6v.

Thank you
 

You may want to check this paper on supply independent cmos current source:

Please press helped button if you find it useful
 

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    surianova

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Hi surianova

The current I in the circuit below have the the value independent to the supply voltage. You can mirror it (using the NMOS transistors) and use it as a current source.

65_1192791113.gif


65_1192791196.gif
 

nassim_el85 said:
Hi surianova

The current I in the circuit below have the the value independent to the supply voltage. You can mirror it (using the NMOS transistors) and use it as a current source.

65_1192791113.gif


65_1192791196.gif
Click to expand...

how to make it independent of resistor and beta?
 

u can use cascode current mirrors
there are three types of cascode current mirrors .. with a liberty of swing that u can want ... low swing and high swing.

these current mirrors mirror to a least extent of error with voltage across the current mirror (obvious : provided all are in saturation region )
 

Just generate a referent current ( as using Vbe/R or Vref/R) then using cascode to get the current independent power supply.
 

harrytrinh is right!

If you want to get a constant current, I think there are so many ways. all can be divide two kinds, first , you get a constant voltage which is independent power supply, then use the constant voltage goes throght a resistance with feedback.

another, you can get two kinds current which are PTAT current and CTAT current, then summing them and mirror output.
 

Using the cascode structures make the current mirrors independent of voltage, but they will eat headroom and need to be carefully oplaced. they can be put in subthreshold also.
 

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