[SOLVED] Integrator circuits that have small capacitors and long integration time

[Moustafa Khatib]

A readout channel for Terahertz FET detector consists of four stages (Gm-c filter, Integrator, Correlated double sampling and S&H). The problem in this design is that I have to use large capacitors in the integrator stage in order to have long integration time otherwise it will be saturated. However that capacitors consume large area and not scalable for designing large focal plane array. What is alternative circuit that can be used as integrator with small capacitor and provide long integration time?

Thanks!

 

[BradtheRad]

There is a circuit known as a capacitance multiplier. It consists of a transistor, arranged to augment the effect of a small capacitor attached to the bias network.

It may fit on a smaller area.

I don't know whether it can be adapted to your purposes, nor whether it will operate at tera-Hz speeds.

 

[dick_freebird]

Another approach which is seeing some popularity in
ROICs is to use a smaller inegrator, and when it limits
you reset the cap and increment a counter. You can
accrue 2^N-1 times the cap value's worth of charge
as a hybrid digital (MSB to LSB-1) / analog (LSB)
combination.