Why not use an analogue switch IC?
DG468 single channel
https://www.vishay.com/docs/74413/dg467.pdf
DG445 four channel
https://docs-emea.rs-online.com/webdocs/1300/0900766b813009f9.pdf
An excellent suggestion, which would work well with a smaller integration capacitor, however Mechatrommer's got very large integration capacitor and the analog switches you suggested are only good for max 30mA, (100mA 1ms pulse), so for the DG468 you'd need a 1K
series discharge resistor to keep it safe, which with a 235uF integration capacitor (2x 470uF back to back) and +/-15V rails, gives a worst case time to discharge of well over one second. Use a DG445, and it can do 30mA per channel - parallel them all each with its own series 1K resistor and it will handle 120mA, which lets you get the reset time down to around 0.28 seconds (to 1% of initial voltage).
That's still pretty poor compared to my back-to-back MOSFETs, as the
BSH114 MOSFETs I selected can handle 3.4A peak for long enough to be useful, and around 0.75A continuous (derated to 50 deg C), which lets you reset the integrator an order of magnitude faster.
The
H11F1M PhotoFET optocoupler Mechatrommer briefly considered is also unsuitable for resetting such a large capacitor - its nominally good for 100mA abs. max. but its output characteristic (fig. 2) shows it will be unlikely to pass more than a few mA. A
TLP175A PhotoMOS relay would be more suitable as that can actually deliver its 100mA rated load current.
... thinking about it, before i send the pcb, i will implement analog switch as well on the pcb along with the triac opto solution, so i can switch between them to see which works better. analog switch has size and component count advantage, so if triac opto does not show significant improvement, maybe analog switch is the solution in the next revision. this can be part of my learning process.
I think your OptoTRIAC idea is going to disappoint you. The OPAMP you are using to cancel its On state voltage drop wont be able to supply enough current for a fast reset, and as Zero999 just pointed out, a MOC3041 has a zero crossing detector so you cant even trigger it with a significant steady DC bias voltage across it.
(I disagree with Zero999: worst case, full windup railing the output plus continued input at the opposite rail you could have over 25V across the integrator cap, 30V if the OPAMPs have rail-to-rail outputs.) A MOC301xM or MOC302xM series OptoTRIAC, without a zero crossing detector would work as a coarse integrator reset. I wouldn't recommend trying to cancel its on state voltage with an open-loop OPAMP as you are likely to run into problems with failure to commutate due to excess dV/dt, unless you limit the OPAMP slew rate + you'll still need a beefy push/pull booster stage after the OPAMP. A better idea would be to pair it in parallel with one of Zero999's suggested analog switches - Fire the OptoTRIAC first to get it 95% of the way to reset and to handle the high current, then use the analog switch to discharge the last few volts.