ethan
Member level 3
output stage current ota
hello everybody,
I got a question for the step response configuration, which I have not thought about clearly.
My opamp is single stage fully differential fold-cascode OTA to drive capactive load. The CMFB is switch capacitor circuit.
When I tried to test step response, I used unity gain feedback configuration (shown in figure (a)) and got expected results. Since, in reality, this OTA need to work with two phase clocks for both SC-CMFB and close-loop configuration, I used figure (b) to test it with clock phase 1 (and both p1 and p2 for internal SC-CMFB with same frequency and non-overlapping). But it seems something wrong here and I couldn't get expected results. The output Vop and Vom are keeping constants in certain values. There is no ramp or slew behavior for the outputs.
So, what's wrong with configuration (b)? Is configuration (c) correct for step response? or other configuration for this step response?
Note: all capacitors are same values and all resistors are greater than 100Mohms.
phase 1 is the resetable phase; phase 2 is the amplification phase.
Appreciate your suggestion.
ethan
hello everybody,
I got a question for the step response configuration, which I have not thought about clearly.
My opamp is single stage fully differential fold-cascode OTA to drive capactive load. The CMFB is switch capacitor circuit.
When I tried to test step response, I used unity gain feedback configuration (shown in figure (a)) and got expected results. Since, in reality, this OTA need to work with two phase clocks for both SC-CMFB and close-loop configuration, I used figure (b) to test it with clock phase 1 (and both p1 and p2 for internal SC-CMFB with same frequency and non-overlapping). But it seems something wrong here and I couldn't get expected results. The output Vop and Vom are keeping constants in certain values. There is no ramp or slew behavior for the outputs.
So, what's wrong with configuration (b)? Is configuration (c) correct for step response? or other configuration for this step response?
Note: all capacitors are same values and all resistors are greater than 100Mohms.
phase 1 is the resetable phase; phase 2 is the amplification phase.
Appreciate your suggestion.
ethan