OTA in dual slope ADC

[salil87]

Hi
I want to use an OTA integrator in a dual slope ADC. But since the input signal is large signal wont it change the gm for different levels?
Thanks
Salil

 

[erikl]

If the input signal stays within the Input Common Mode Range (ICMR), and this ICMR range is defined by a gain loss of e.g. -1dB (see the PDF below, -3dB in that case), the variation should also stay within this range (-11% in this case).

 

[crutschow]

If it's the common inverting integrator with a capacitor from output to the minus input and the plus input is to common, then the input CM voltage is zero and the ICMR isn't a factor. Also with the typical high open-loop gain of an OTA, any change in gm would have no significant effect on the closed-loop signal.