[sdiy] Killing OTAs [was: Re: SEM LFO square wave mod...]

[lanterma at ece.gatech.edu]

On May 27, 2011, at 9:57 PM, Paul Perry wrote:

> Anyone playing around with a CA3080 - or any similar OTA like the LM13600 - needs to know that the maximum curren tthat can go into pin 5 is 2mA.
> DO NOT connect it directly to a voltage, that will kill it stone dead in a microsecond.
> I always connect a 10K resistor to pin 5 (or the equivalent pin) because that prevents current overload, no matter what you connect it to. It isn't a control voltage input, it is a CURRENT control input.
> By running voltage through the resistor, you make it look roughly like a voltage control.

The lab project part of my class is largely defined by students killing OTAs when they're poking around their circuit - it's a veritable 13700 grave yard. ;)

Sometimes when you blow an OTA you can tell by taking a DC reading at the current control pin. It should read about a volt about the negative rail; if it doesn't it's blown. 

- Aaron