what power supply? the one that gives the op-amp rail supplies? how is that affected by C213??
and a more general question, what really is the purpose of C213? could you explain better the charging and discharging of that capacitor?
In my opinion, "stability problems" are not identical to "instability". Rather, "stability problems" can mean that the step response exhibits ringing (decaying oscillations) due to a small phase margin.
However, the circuit is still stable - according to the final value theorem.
Hi all, basically my problem is this..il explain it: i have Analog input Card (4ma-20ma) which had a CPLD in it which become obsolete. so it was change to just IC, few IC's to stimulate the same circuit as in the CPLD. anyway this modifications should not disturb the analog part as it is isolated by optocoulers.
So what happen is, The AIM card have active mode (in which the sensor connected will be powered by internal AIM board Isolated 24vdc power supply) and another mode:- passive mode (in which the AIM card will be powered by the external power supply)
now after the modification the new board (without the CPLD) have this "instability" problem when used, while the old board is more stabil, although the ANALOG CIRCUITRY are the same. i dono why
after measure all the signal:- along the analog signal chain, this what i got:- refer the table i attached below in forum:- (this reading taken at the op-amp(follower) which i attached at the first message.
seems all the voltage are consistent along the analog signal chain until reach this voltage follower op-amp circuit where the input and output is not same.
View attachment 65139
so now yes im having instability problem where the voltage follower op-amp have slight difference in between the input voltage and output volatage, and because the ADC resolution is very high..small variations also giving me different results..although the board is injected with same analog input current.(4-20ma)
when use in active only the voltage follower op-amp have higher variance between Vin and Vout, so basically let say i calibrate the board using active mode when i switch to passive mode i need to re-calibrate again...but logically i just need calibrate one time in either 1 of the modes.
so is it good idea the remove the C213 capacitor, anyway il try remove it and retest again..see what i get.