output buffer

[peter purpose]

[quote author="clintrubber"] What were your thoughts ?
Just curious.

[/quote]

Simplicity. I looked at the api summing circuit and thought that'll do me.

peter

 

[clintrubber]

[quote author="peter purpose"][quote author="clintrubber"] What were your thoughts ?
Just curious.

[/quote]

Simplicity. I looked at the api summing circuit and thought that'll do me.

peter[/quote]

That's a reason that sounds as good as any :thumb:

Peter

 

[PRR]

> the 2520 as shown has a discrete BJT input ...

IIRC, the 2520 has a resistor long-tail(?). It can't be swing to its output limits when working as a non-inverting follower. Swing negative, input pair current goes to zero; swing positive, pair current doubles which will force one side very rich. Very asymmetric. It has to be worked hi-gain noninverting, or inverting. Small common-mode voltages only.

And it has enough input current noise for the 100K resistors to be a noise source: going 33K is probably wiser. If you cut all that other stuff off the output of the poor TL07x, you could go 10K.

 

[peter purpose]

Cheers Paul,
The op-amp I was 'really' going to shove in there is a 2520 footprint 5534 with added driver circuitry, which works really well in a 2520 application.

I was toying with the idea of losing the TL081 completely and coming straight off the fader.

peter

 

[NewYorkDave]

2520 footprint 5534 with added driver circuitry

Sounds interesting. Got a schematic?

 

[peter purpose]

[quote author="NewYorkDave"]
Sounds interesting. Got a schematic?[/quote]

I haven't Dave, but give me a few days and I'll try to sort it.
I unpotted this thing a while ago out of curiosity and found a 5534 in there.

peter

 

[gyraf]

WHAT was that, before it got unpotted? :shock:

 

[peter purpose]

 

[gyraf]

:wink:

 

[clintrubber]

[quote author="bcarso"]Oh sure---you can still get common-mode distortion from a discrete bipolar input.[/quote]

[quote author="PRR"]> the 2520 as shown has a discrete BJT input ...

IIRC, the 2520 has a resistor long-tail(?). It can't be swing to its output limits when working as a non-inverting follower. Swing negative, input pair current goes to zero; swing positive, pair current doubles which will force one side very rich. Very asymmetric. It has to be worked hi-gain noninverting, or inverting. Small common-mode voltages only. [/quote]

Right, the story is like this.
Initially I confused myself by looking for alike mechanisms as for those JFET-inputs, but IIRIC the 2520 has indeed just a resistor and not a 'real' current source there.

 

[peter purpose]

This is how api build 2520s

This will self destruct in 10 minutes......


TOO LATE

 

[kruz]

I was too late

 

[peter purpose]

This is how a 2520A5As input is donedid.

 

[clintrubber]

Could that 2520 have been the DOA with the most variations ?

FWIW, the schematic I saw had just a 150k tail-R, must have been an older version.