Circuit Design Help

[737NUT]

Hi all,
I need to design a circuit that does the following, I need to drive an instrument that has an op amp on it's signal input. 2 wires, one is ground the other is the input which has to go from -550uA to +550uA I would like to use a PWM output from a microcontroller to to send this varying signal to the input of this gauge. I know i'm going to have to use an op-amp driven from the PWM output of microcontroller but not sure how to make it swing from neg to pos or vice versa and at that low of current. Is this at all possible via PWM?
Thanks
Rob

 

[crutschow]

You can use PWM with the common side of the gauge connected to 1/2 the supply voltage (can be generated with a simple resistive voltage divider).
That way a 50% duty-cycle will give an average output of zero to the gauge.

 

[737NUT]

Hello,
Thanks for the reply. I am already doing that now, see sketch below. I need another volt to 1.5volt as the arduino i'm using is only a 3.3V pwm output. I'm getting -1.6Vdc one way and +2.0Vdc the other way.

 

[crutschow]

Your schematic is confusing.
Exactly how is the meter connected?