[sdiy] Problems with linearized SSI2164 ?

Mattias Rickardsson mr at analogue.org
Thu Feb 14 21:52:57 CET 2019


Den tors 14 feb. 2019 20:49 skrev Dave <dlmanley at sonic.net>:

>
> This is a GBW/ phase margin issue?  Indicating the SSI part has greater
> GBW so is less tolerant to a reduced cap value?
>

Maybe? Or is it the op-amp that matters?

Anyway, the circuit had values outside the recommendation. We shouldn't
expect makers of drop-in replacements to specify how their product behaves
versus the original in an unrecommended application.

Btw, we're actually touching one of the hidden advantages of the SSI part:
With the old 2164s in the ordinary VCA configuration with 30k resistors,
one might be tempted to use quite small feedback caps in order to not
introduce noticable HF roll-off under 20 kHz. With the doubled current
capacity of the SSI2164 the resistor values can be halved (for reaching the
lower noise specification), meaning that the cap value can be doubled for
the same roll-off. So in practice, perhaps even better tolerance for the
needed cap values. :-)

/mr
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