How to make a simple transimpedance amp

Well, the simple method would be to wire it as a transimpedance amp with a 10k feedback resistor, and then sink 1 mA from the summing junction to the negative supply, or a negative voltage reference if one is available. I'd probably want to use a diode in series with the DAC current output, and another one from the summing junction to ground (anode grounded) just to make sure I didn't blow up my MCU if I lost one of the analog supplies.

Cheers,

Phil Hobbs

I must be missing something, this is basic stuff. You want 0-2mA to give

-10 to +10V. That's a 20V swing, so an inverting opamp with a feedback resistor of 10k will do the job. But that's 0 to -20V, so you need to offset it by 10V, or 1mA at the input. You've got -12V, so a 12k from the summing junction to that gives you the offset you want.

The 0-2ma signal is being generated by a DAC onboard a

So why is it 0-2mA?

Hi Phil - your idea seems just about right. Somehow I hadn't really thought about diverting current like that.

One thing that has been bothering me: Would it be necessary for me to put a resistor inline between the microcontroller DAC output and the summing junction? If I didn't, the DAC output would have 0V at it's output. I do not know if this would bother a DAC or not.

Thanks,

-Michael

Is it a VOLTAGE or CURRENT ouput DAC?

Nope - I think I was the one missing something :). Your suggestion seems exactly right.

It is a current output DAC.

-Michael

That would depend on the DAC, but I'd think it would be odd for a single-supply device to be bothered by that. In any case, the protection diodes I suggested would move the DAC output voltage up to about 0.7V.

Cheers,

Phil Hobbs