I'm testing a design in which I need to do a current to voltage conversion. The current ranges from picoamperes to 100mA (both positive and negative), so I use 4 different resistors and a switch to select each of them. I filter the corresponding signal (not shown in the image), use a variable gain (x1, x10, x100, x1000) amplifier and then adapt it and detect it.
Everything works perfectly fine till 20mA, the op amp output current limit. Can anyone please show me a simple power stage that can be used preferibly inside the feedback loop? The output voltage has to be between -5 and +5 volts and has to work for +-100mA. 
