[sdiy] Discrete Op Amps

[Mattias Rickardsson]

On 10 April 2017 at 08:51, Gordonjcp <gordonjcp at gjcp.net> wrote:
>
> You just need to use the TL07x family, unless you've got ridiculously specialised needs.

There is no point in looking down upon specialised needs.

> When you open up a synthesizer (a proper one, not one of those silly "boutique" modules) have a look at what opamps it uses.
> I bet you'll find it's full of TL07x opamps, or something at a similar price point.

Any serious designer chooses different OP amps based on different
needs. There's lots of TL07x in synths because it gives the most
bang/buck - in the applications where it's appropriate! There are very
typical places in synths where I've found it's *not* very appropriate
(and they are not even near hi-fi aspects or subtle nonlinearity
factors) :

- Voltage followers or noninverting stages where there is a risk of
high common-mode voltage, because TL07x suffers from phase inversion.

- Tiny codec signals sometimes need a lower noise op-amp, depending on
the circuit solution.

- Situations where a higher noise and a lower slewrate is acceptable:
here you can save lots of power by using TL06x instead of TL07x.
Applications such as CV multiplexing, CV processing, and even VCO
cores! (where you always have max level and always run the signal
through higher-noise circuits downstream)

/mr