Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

how to low the noise of amp

Status
Not open for further replies.
rainman.cn

rainman.cn

Member level 2
Joined
Feb 27, 2007
Messages
42
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Activity points
1,510
hi, everyone,
I use the circuit as shown in the pic.
when i increase the Cfb, the noise cannot decrease as predicted,
because the output stage dominate the noise performance when Cfb is large.
how can i solve this problem,

my amp is simple two stage amp with first stage fold-cascade and second stage common-source .

thx,
 

I think, it's usual to refer noise to amplifier input. I can't see, how a Cfb can decrease noise then. Measures of noise reduction are to my opinion:
1. Noise matching of input transistor operation point to source impedance
2. Minimizing additional noise sources in the circuit
 

FvM said:
I think, it's usual to refer noise to amplifier input. I can't see, how a Cfb can decrease noise then. Measures of noise reduction are to my opinion:
1. Noise matching of input transistor operation point to source impedance
Click to expand...

may you explain the first ponit in detail, thanks!
 

What kind of noise you talking about? The opamp noise? For my understanding, opamp noise can't reduce by any external component. BTW, to simulate the noise, it should use resistor to feedback rather than capacitor.
 

The noise of a two stage amp is set by the feedback factor and compensation capacitor. Increase Cc to get lower noise.

Bastos
 

FvM said:
I think, it's usual to refer noise to amplifier input. I can't see, how a Cfb can decrease noise then. Measures of noise reduction are to my opinion:
1. Noise matching of input transistor operation point to source impedance
2. Minimizing additional noise sources in the circuit
Click to expand...

Hi, how to realize the noise matching?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top