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

[Chris Juried]

I generally use an LM4562NA in my first and second stage if applicable. This Op Amp has an exceptionally low input noise voltage of 2.7nV/√Hz along with excellent distortion characteristics. Douglas Self has done a write up on the LM4562NA along with various predecessors, such as the NE5532, etc. 
  Sincerely,   
  Chris Juried  
Audio Engineering Society (AES) Member  
InfoComm-Recognized AV Technologist
http://www.JuriedEngineering.com (Juried Engineering, LLC.)
http://www.TubeEquipment.com (Tube Equipment Corporation)
http://www.HistoryOfRecording.com (History of Recording)


This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any distribution or copying of this email, and any attachments thereto, is strictly prohibited. If you have received this email in error, please immediately notify me and permanently delete the original and any copy of any e-mail and any printout thereof.

 

      From: Roman Sowa <modular at go2.pl>
 To: synth-diy at dropmix.xs4all.nl 
 Sent: Friday, January 29, 2016 7:06 AM
 Subject: Re: [sdiy] Spare op-amp useful in gain stage?
   
Opamp noise is referenced to its input, so whether it's amplified by 
30dB and then abother 30dB, or by whole 60dB in one go, overal noise 
should remain the same.
Distortion also increases with gain, so that's another reason to split 
it to 2 lower gain stages.
OTOH there are application when it's better to have one high gain stage.
There's no single rule for everything.

Roman

W dniu 2016-01-28 o 19:41, Tom Wiltshire pisze:
> 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
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>>
>>
>> --
>> Quincas Moreira
>> Test Pilot at VBrazil Modular
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20160131/9fa3913e/attachment.htm>