TL071/TL081

[Grant Richter]

As far as semi-conductors go. There are only so many die types, and doping
is still a somewhat uncertain process. A number of different parameters are
going to have Gaussian (bell curve) distributions around the center target
point. But you don't want to have to throw away dies outside some
percentile. You just assign them a different part number with a relaxed
spec.

In the old days, they would take a batch of transistor die and "test" them
into part numbers. That is they would check the die test results against
multiple specs and slap a part number on the ones that passed for that part
number. So the same die might appear as several part numbers.

I could be wrong, but I believe that's how 2N3905/2N3906 (higher betas are
3906) CA3045/CA3046 (higher betas as 3046) and so forth. Basically splitting
the bell curve and assigning two different part numbers to the upper and
lower half, and charging more for the better results.

Maybe the 1N400x series are also like that, a 1N4001 is a 1N4002 die that
tested below 100 volts, so now it's rated at 50 volts but might actually
have a breakdown voltage between 50 and 90.

I had always assumed the TL07x were the lower half of the bell curve for
TL08x sorted for noise figure. The noisier die that still pass DC spec are
labeled 08x and the quieter ones 07x, but otherwise are the same die?

----------
>From: Jim Patchell <patchell at silcom.com>
>To: Tim Curtis <sexsymbol at execpc.com>
>Cc: AH <analogue at hyperreal.org>, synth-diy at node12b53.a2000.nl
>Subject: Re: TL071/TL081
>Date: Thu, Nov 9, 2000, 8:54 AM
>

>     In my opinion, the two are pretty much interchangeable.  The 07x seriers
> has a slightly quieter front end, and I believe the output stage is biased a
> little heavier to give better distortion.  In general, I have used the two
> interchageably.
>
>     -Jim
>
> Tim Curtis wrote:
>
>> Can anyone really explain to me what the difference is between these two
>> op-amps?
>>
>> One of my MiniMoog Oscillator boards was diagnosed as having a bad
>> TL081.  I replaced it with a TL071because I have some of those around.
>> Nada.
>>
>> Is this normal?  I was always told that the two were pretty much
>> interchangeable.
>>
>> Or is it just a problem with them in that circuit?
>>
>> Tim
>
>