Hi,
Based on some previous posts, I need to build an op-amp subtractor (Error = Vref - Vfeedback) feeding an op-amp control-loop.
I am pondering the trade-off of a single-supply subtractor / control- loop vs. a charge-pump + standard op-amp control-loop. Op-amp based control-loops are challenging for me already, the single-supply part is additionally tough for me.
I have available a 200 kHz freely running 50% duty cycle signal, with a PFET/NFET (buffer) + diodes + cap I can probably generate a negative supply rail.
Question is, is the noise generated by the charge-pump (even with heavy filtering, say a 100 uF capacitor) going to severely affect the op-amp circuit? I expect 20 Hz 0 dB open-loop BW for control-loop.
Any thoughts on using charge-pumps and their effects on noise for op-amp circuits would be appreciated.
Rob.