Following on from this question:
I have the task of setting a voltage V_set using PWM. The challenge arises from the fact, that V_set is referenced to a different ground than the MCU.
My currently best solution is the following.
Can somebody suggest improvements? I am particularly always happy to simplify things when possible...
I realise that the first opamp may oscillate a bit during slow transitions. My feeling is that this would be acceptable, since it will be filtered by C1.
- How small can I make C1 before I run into problems? (I was considering R3=1M & C1~160pF.)
- In the context of this circuit, is there any real advantage to capacitively decoupling the reference voltage of the first opamp? (Lower leg of voltage divider.)
- No I really need R4 & R5? (Then V_CB could reach -7V.)