OPA376: DAC Controlled current source.

HARI T O1

Expert 1675 points

Part Number: OPA376

Tool/software:

Hi,

I am designing a current source based on ths document from TI.

My VDAC is 3.3V and Iout is 20mA.

Not getting the required current

May I know where I went wrong.

Regards

0 Clemens Ladisch over 1 year ago

Guru 322980 points

That output current is correct for your resistor values. To get 20 mA for a 3.3 V input, R3 must be smaller. Which formula did you use?

+1 Marek Lis over 1 year ago

For R3 of 322ohm you got a correct IOUT of around 4mA - see below.

In order to obtain 20mA IOUT, you must use following formula: AM2*R2 = IOUT*R3 where AM2 = AM1*beta/(Beta+1)

This results in R3 of around 65ohm - see below.

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