Hi all!
In order to avoid dc at the output of preamps you have about 3 choices:
(I'm talking about preamps that can drive low impedance loads,
like 1k and below, and also has variable gain):
1) Use electrolitic capacitor at the output, and it has to be quite
big if you don't want some bass roll.
2) Use some king of a servo to null the dc at the output.
3) Design a perfect circuit with perfectly matched parts in
order to avoid dc from the beginning.
Well, I don't like options 1 and 2, and option 3 is quite difficult
to obtain (at least for me), specially when the gain is variable.
So I thought why not use a PREAMP-CAPACITOR-BUFFER circuit,
so the capacitor can be a high quality small value one (because
of the hign Z of the buffer), and the buffer is unity gain so
it can be easy to obtain zero offset for dc-coupled output.
I'm not trying to avoid capacitors at all, but just electrolitics.
I'm sure I'm not the first one who thought about that, but I haven't seen circuits using this method, so I wonder if it has shortcomings that I haven't thought of?
Udi.
In order to avoid dc at the output of preamps you have about 3 choices:
(I'm talking about preamps that can drive low impedance loads,
like 1k and below, and also has variable gain):
1) Use electrolitic capacitor at the output, and it has to be quite
big if you don't want some bass roll.
2) Use some king of a servo to null the dc at the output.
3) Design a perfect circuit with perfectly matched parts in
order to avoid dc from the beginning.
Well, I don't like options 1 and 2, and option 3 is quite difficult
to obtain (at least for me), specially when the gain is variable.
So I thought why not use a PREAMP-CAPACITOR-BUFFER circuit,
so the capacitor can be a high quality small value one (because
of the hign Z of the buffer), and the buffer is unity gain so
it can be easy to obtain zero offset for dc-coupled output.
I'm not trying to avoid capacitors at all, but just electrolitics.
I'm sure I'm not the first one who thought about that, but I haven't seen circuits using this method, so I wonder if it has shortcomings that I haven't thought of?
Udi.
Attachments
Your block diagram seems has appeared in some1's article on designing low distortion power amplifier,but i cant recall who's article.
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