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Design >> Analog Design >> Help: Overheating op-amp in state-variable filter!
https://designers-guide.org/forum/YaBB.pl?num=1406192742

Message started by itoqixer on Jul 24^th, 2014, 2:05am

Title: Help: Overheating op-amp in state-variable filter!
Post by itoqixer on Jul 24^th, 2014, 2:05am

I am trying to build an audio-frequency state-variable resonant filter.

Power supply is ±15V. The circuit contains three TL072 op-amps and three LM13700 OTAs. It receives audio input from -2.5V to +2.5V and outputs a filtered signal depending on its cutoff frequency control voltage. This part works perfectly.

Decreasing the voltage on REZ from 5V to 0V should introduce resonance.

Here's the problem:

When I try to decrease the resonance control voltage (REZ), it works for a while, then stops outputting sound, starts drawing way too much current, and IC13 heats up.

I would sincerely appreciate if someone could help me debug this or offer any suggestions.

Thanks in advance.

Title: Re: Help: Overheating op-amp in state-variable filter!
Post by loose-electron on Jul 24^th, 2014, 7:01pm

Schematic?