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PSoC 5, 3 & 1

Not applicable

Will the opamp in PSoC 3 be stable in follower mode with upto 100 microfarad of load capacitance?




With a 100MFD load, the opamp (in voltage follower mode) will be stable.


But it will have reduced bandwidth and hence, reduced slew rate. Phase margin is also very low leading to a longer settling time.

2 Replies
Esteemed Contributor

It might be advisable to consider the effects a 100 mFD capacitor has


discharging thru output parasitic diode when Vdd falls to ground. Thats the


only discharge path C has and its thru a very small area (junction) diode.


And of course 100 mFD cap has a lot of charge in it, and potentially very


low ESR, read high currents result.




Regards, Dana.

Not applicable

There is another issue with such high C load.




The OA stability may have been analyzed with output routed


directly to a pin. But if we employ routes thru muxes and other


components, out to a pin, then hang 100 mfd off pin, and take our


feedback from the pin, we have added a lot of phase shift due to


route R, and stability and phase margin will rapidly decline.




Useful reference -




Regards, Dana.