LF411 Op-Amp dilemma

gstopp at fibermux.com gstopp at fibermux.com
Wed Jan 22 18:20:44 CET 1997


     On 1/22/97 radioactive at geocities.com (brad sanders) wrote:
     
     >
     >I can't think of an application for the 3140 that can't be done 
     >better by another device. Frankly, I wouldn't use a 3140 in a piece 
     >of gear even if someone gave me a tube of'em.
     >
     
     I have yet to find a chip that works better in integrator applications 
     than the CA3140. The TL081/2/4 is my favorite all-around op-amp, it's 
     true, but the 3140 beats it in VCO's and VCF's. The extremely high 
     input impedance (unrivaled, I believe) means that the low end of the 
     integrator's range can be extended way into the sub-hertz region, yet 
     still extend way beyond the audio range at the other end without 
     switching in a different cap. This advantage outweighs the fact that 
     the 3140's output must be buffered before it ever sees the end of a 
     patchcord due to it's inability to drive standard 1K bipolar loads.
     
     Yet another drawback to the 3140 is that it's easily blown up by ESD. 
     I have never seen such a wimpy chip, so you ASM-1 builders out there, 
     beware! Use your wrist strap. It's the price you pay for the delicate 
     input on the thing.
     
     If you have tubes of them you don't want, can I have them?:)
     
     There are other op-amps out there that seem unlikely candidates for 
     anything since they're so old, but seem to do the best in some 
     particluar niche anyway. For example, Electronotes was very fond of 
     using the 748 in comparator applications like square and pulse wave 
     outputs, and darned if I can't find a chip (even the TL082) that makes 
     snappier rectangles. The 748 is an uncompensated 741, as lowly as that 
     sounds.
     
     I agree with whoever it was that said that a nice comprehensive op-amp 
     comparison chart would be cool. There was such a chart in "The Art of 
     Electronics", but alas in my zeal to spread the joy of designing I 
     lent it out and never got it back (like my copy of Jung's "Op-Amp 
     Cookbook" - geeeez what a sucker I am). Anyway an updated chart is in 
     order, what with all the AD and SSM and LT and whoever else stuff out 
     now...
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: LF411 Op-Amp dilemma
Author:  radioactive at geocities.com (brad sanders) at ccrelayout
Date:    1/22/97 1:12 AM
     
The CA3140 is a very poor sub for an LF411. In many apps, it will NOT, in any 
way, perform as a "drop in replacement."
     
I can't think of an application for the 3140 that can't be done better 
by another device. Frankly, I wouldn't use a 3140 in a piece of gear 
even if someone gave me a tube of'em.




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