Optikon said:
Ron H said:
Here is a way that does no lowpass filtering on the input. It is a little more complex.
I've attempted to do precision slew control with a similar circuit in the past. It used the same current sources through diodes to a capacitor idea. I couldnt reconcile the fact that the diodes would not equally share the current (and hence error in slew control) this certainly fell apart over temperature. Balancing the voltage on both sides didnt entirely eliminate the issue either. Other than matched diode pairs, do you have an idea for making this precision (like .01% control)???
During slew rate limiting, only 2 diodes are on. For example, if the input is rising faster than the capacitor can charge, only D2 and D3 are conducting. Mismatches do not cause slew rate imbalances. Matching is only an issue when slew rate limiting is
not occurring. If diodes are mismatched, you then have a DC offset between input and output. Is this what you are referring to? If so, the only suggestion I have is matched diodes, such as CA3039. Current source mismatch will cause slew rate imbalance between positive and negative slopes, and will also cause an offset error.