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No. The speed is not decided by rout. It is decided by the bandwidth.leohart said:I was confused whether the charge speed is decided by rout of the OTA(which is big) multiply by C or gm/C?
I think the speed is only related to rout*C in linear settling situation,will an OTA has a big output resistence also have a very slow speed when driving a cap?...and what is gm/C?
Hughes said:No. The speed is not decided by rout. It is decided by the bandwidth.leohart said:I was confused whether the charge speed is decided by rout of the OTA(which is big) multiply by C or gm/C?
I think the speed is only related to rout*C in linear settling situation,will an OTA has a big output resistence also have a very slow speed when driving a cap?...and what is gm/C?
For a constant input voltage the voltage across the feedback C would rise linearly, however, since the input voltage drops, there will be an increase of the output voltage following an exponential function.
Sorry, I did not express myself clear enough. "Following an exponential function" means, of course, following the function (1-exp) . That means - similarly to charging a cap through a resistor - the voltage across the feedback capacitor (identical to the output voltage of the OTA) reaches a final value which depends only on the input voltage as well as the cap ratio.