Originally Posted by robz

Got a question about converting voltages.

i've got a +3.3V pwm signal out of my CPLD, convert it with a RC network to a maximum analog voltage of +3.3V (duty cycle 100%).

Now i'am going to use the signal for creating an offset signal after a DAC circuit.

This offset must be about -5V or +5V.. it also may be a little bit lower (4V should also work).

so i want to convert the analog voltage of the RC network (0..+3.3V) to a range of -5V..+5V.

Somebody got an idea how to do it? thank you...

Do you have +/- supplies? You will need at least +/- 5V. +/-7V or higher will give you a wider choice of op amps. I'll try to post a schematic after you answer.

This circuit's output will swing within millivolts of the supply rails. The input impedance is very high, so your input can come directly from your PWM filter.
If your +5V supply is accurate and stable, you can use the bottom circuit, instead of requiring the LM336.
You can use a different op amp, so long as its output can swing rail-to-rail and it can handle +/-5V supplies.