You might post youir project so forum can take a look at it.
When you say "The differentiator's o/p starts at 1.6V rather than 1.25V.",
is this for input floating ? What is the size of the Rfeedback used on
differentiator ? Is bias current creating a large offset ? Or is this just
creating a follower out of OpAmp, hence with input floating the differentiator
will be at Vdd/2 ?
Couple of points to check:
1. What is the power settings and the column clock frequency? Please see application note - AN2223 (PSoC 1 Approximating an opamp with switched capacitor integrator) - http://www.cypress.com/?rID=2630 for guidance.
2. If input is floating, the approximated opamp, will act as a voltage follower (with a resistor connected between -input and output). But the output voltage will depend on the CA, CB capacitor values. See equation 8 in AN2223. If the feedback resistor is too high, it can affect the output voltage too, depending on the column clock frequency.
For the comparator question: SCBLOCK, approximated as opamp, can only work if operated in a closed loop system. Otherwise it is a pure integrator. Please follow cookbook provided in appendix of application note AN2041 (http://www.cypress.com/?rID=2899) to know the parameters for comparator configuration.
Thanks a lot!