Appearance amplifier noise

Appearance amplifier noise

[introduction] because appearance amplifier basically is used at enlarge tiny and accurate signal, accordingly, be necessary to know the effect of source of all and relevant noise. Following face figures show appearance amplifier model 1 times.
 
Appearance amplifier noise
 
Input voltage noise has two source. The first origin expresses to be the noise source V that carries series with the inputNI, in be like circuit of groovy operation amplifier same. This noise reflects output end by G of appearance amplifier gain. Source of the 2nd noise is output noise VNO, show the noise tension that establishs ties to output end with appearance amplifier. Output noise (express to be V hereOUT) can pass except with gain G, thereby amount to is carried to the input.
 
With I of input noise electric currentN+With IN–Associated noise source also has two. Although IN+With IN–Normally equal (IN+ ≈IN– = IN) , but they are not relevant however, accordingly, the noise that both place produces must in order to mix root (the means sue for peace of RSS) . IN+Had shed RShalf, IN–Had shed other in part. The result can produce two noise tension, its extent is I eachNRS/ 2. Source of these two noise reflects output end by G of appearance amplifier gain respectively.
 
Total output noise is through mixing root form is opposite all of the means cipher out of sue for peace of 4 noise source.
 
Appearance amplifier noise
 
Requirement total noise (amount to is carried to the input (RTI)) , need to remove afore-mentioned expression only with G of appearance amplifier gain can.
 
Appearance amplifier noise
 
Manual of appearance amplifier data connects regular meeting to express RTI of total voltage noise to be the function of gain. Noise spectrum density includes an input at the same time (VNI) with output (VNO) noise contribution. Input density of voltaic noise spectrum to set apart.
 
if be in operation amplifier, must be RTI of noise of total appearance amplifier inside bandwidth of closed circuit of applicable appearance amplifier undertake integral, thereby cipher out is worth with root. Bandwidth can decide according to data manual model, answer frequency the function that expresses be gain among them.
 
To this bandwidth, wu takes care surely when computation, because its are not constant normally,bandwidth accumulating concerns (if VFB operation amplifier is such) namely. To series of AD620 appearance amplifier, gain bandwidth mode more resemble amplifier of operation of a CFB. Below this kind of circumstance, forecast giving the way with the safest bandwidth below gain is the curve that offers in service data manual.
 
Bibliographical reference
 
1.Hank Zumbahlen, basic Linear Design, analog Devices, 2006, ISBN:0- 915550-28-1. See Linear Circuit Design Handbook additionally, elsevier-Newnes, 2008, ISBN-10:0750687037, ISBN-13:978-0750687034. Chapter 2.
 
2.Walter G. Jung, op Amp Applications, analog Devices, 2002, ISBN 0-916550-26-5, see Op Amp Applications Handbook additionally, elsevier/Newnes, 2005, ISBN 0-7506-7844-5.Chapter 2.
 
3.Charles Kitchin And Lew Counts, a Designer”s Guide To Instrumentation Amplifiers, 3rd Edition, analog Devices, 2006.  
 
 

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