[sdiy] The TL072

[Simon Brouwer]

Ingo Debus schreef:
>
> Am 20.02.2009 um 19:59 schrieb Antti Huovilainen:
>
>> On Fri, 20 Feb 2009, Ingo Debus wrote:
>>
>>> I once replaced the opamp in the summing amp in my DIY 12 input 
>>> mixer (5534 vs TL072) and got noticably less noise. The summing amp 
>>> has a gain of only 1 for each input, but with 12 inputs the noise 
>>> gain is 13.
>>
>> Do you mean sqrt(13)? (the noise inputs are not correlated and hence 
>> you need to add the power, not voltage)
>
> No, I meant the noise gain, not the noise itself.
>
> AFAIK noise gain is defined as
> G_n = 1 + R_fb/R_in
> with R_fb = feedback resisitor and R_in = all input resistors in 
> parallel for an inverting summing amplifier. For a single-input 
> noninverting amp, noise gain and gain are equal.
> Hope this definition is correct, I can't find a reference right now.
http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=7164

-- 
Vriendelijke groet, 
Simon Brouwer. 

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