[sdiy] Spare op-amp useful in gain stage?

[Tom Wiltshire]

Plus the second amp is going to be amplifying the noise from the first. Is that better or worse than having one op-amp with very high-gain amplifying it's own noise?

On 28 Jan 2016, at 17:37, Quincas Moreira <quincas at gmail.com> wrote:

> I would expect signal to noise ratio to be worse, but distortion to be
> less using Roman's two opamp idea.  Probably not by much, but each
> opamp stage would add a tiny bit of noise...  Am I wrong?  I usually
> go this route when I need high gain, two stages....
> 
> 
> 
> On Thu, Jan 28, 2016 at 7:43 AM, Michael Zacherl
> <sdiy-mz01 at blauwurf.info> wrote:
>> 
>> On 28.Jan 2016, at 13:36 , Roman Sowa <modular at go2.pl> wrote:
>> 
>>> In high gain application it's better to split to 2 opamps, this way you get much higher bandwidth than when done on single opamp.
>>> For example if 60dB gain on one opamp would have 3dB bandwidth ending at about 10kHz, while 30+30dB on 2 opamps of the same kind it jumps over 300kHz.
>> 
>> hm .. so what’s the impact on the SNR?
>> 
>>> W dniu 2016-01-28 o 13:03, Mattias Rickardsson pisze:
>>>> Hi!
>>>> 
>>>> I was in a discussion about what to do with a spare OP-amp. These
>>>> fellows come in duals and quads, and sometimes the quantities don't
>>>> end up perfectly and you stand there with an extra unused op-amp.
>>>> 
>>>> Is there any clever way of using two op-amps instead of one in, say, a
>>>> noisy high-gain stage in order to reach lower noise or something like
>>>> that?
>>>> 
>>>> Douglas Self's small signal book suggests paralleling two gain stages
>>>> ("multipath amplifiers"), having their outputs tied together with 10
>>>> ohms to the destination, winning 3 dB SNR. Are there other clever ways
>>>> of using a spare op-amp, particularly in a stage with high gain?
>> 
>> 
>> --
>> http://mz.klingt.org
>> 
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> 
> 
> 
> -- 
> Quincas Moreira
> Test Pilot at VBrazil Modular
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