Hi Support team
My customer want to add a cap across the resistor from gate to cathode. there is another resistor from gate to anode. The question is, with this cap, when the circuit is discharged, he is seeing current injected into the gate in excess of 50uA
Here is his question
We all know that the output voltage for this part is Vout = Vref · (1 + R1/R2). It is also clear that the part’s noise and dynamic impedance suffers (especially as frequency rises) in proportion to the factor 1 + R1/R2, because of the reduction in negative feedback.
This phenomenon could be ameliorated at AC frequencies by bypassing R1 with a capacitor. Unfortunately, with an abrupt turn off in which Vout suddenly falls to zero volts, this scheme runs afoul of the Abs Max limit which is the subject of this email.
I have an idea for how to get around this problem, but I’d like to better understand the nature of the limit. I assume that the reference voltage at which this negative current begins to flow is somewhere around -.6V, where a substrate diode begins to conduct. I also suspect that a very short -50uA pulse would not cause damage, but that a continuous -50uA would, as would a larger magnitude current of finite duration. Is there an energy limit associated with this failure?
Regards
Jeff Coletti
