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TL074 temperature limits
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prgdeltablues



Joined: Sep 25, 2006
Posts: 222
Location: UK
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PostPosted: Fri Nov 21, 2014 5:53 am    Post subject: TL074 temperature limits Reply with quote  Mark this post and the followings unread

Just finished building Thomas Henry's Controller LFO. During debugging, I noticed the core triangle waveform was often distorted or even that the oscillator failed to run. My workshop is a wooden hut, unheated, except whenI'm working in it. Outside temperature here in the UK round about 6-10 C. I found out that pointing a fan heater at the circuit board for a short while made the oscillator run just fine. There wasn't any condensation, and the rest of my modular sitting out there works OK. Checking the datasheet for the TL074, which is at the heart of the oscillator, I saw it was spec'd only down to 0C. As TH notes, the LFO would tend to stall at very low frequencies anyway, so my guess is that the circuit is operating at the margins of the op-amp's ability, and running it right down near its spec limit was just too much to ask.

Anyone else had a similar experience? - it wasn't half frustrating til I found the solution!

Peter
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JovianPyx



Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
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PostPosted: Sun Dec 21, 2014 1:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

That does seem odd. I've never experienced running them at 0 degrees C. But indeed, I just checked the datasheet and the lowest cost units are spec'd at 0 to 70 C. In my own experience, heat is usually the enemy, not lack of it. I'd never thought about what happens when it tries to run below the low temperature spec., but I guess your experience shows what can happen.

Very interesting, thank you for posting this.

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