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.

questions about noise power calculation

Status
Not open for further replies.

airboss

Member level 3
Joined
May 1, 2006
Messages
64
Helped
6
Reputation
12
Reaction score
2
Trophy points
1,288
Activity points
1,821
Hi,

I have some questions about noise calculation.

1) we know if a transistor or a resistor is tied with a capacitor, the total noise power is kT/C. my question is, could the C be an intrinsic capacitor of a transistor?

2) the following question is for a on-going project. i really need some clues. the schematic is attached as follows. it is a sense amplifier. i want to see at which time point would the noise cause an error at the output. my advisor asked me to find the mathematical solution of input referred noise and then do the simulation.

here's my question. how should i do it? i think there're two possibilities.
a)at point A & B, they're acting like capacitors. A & B are close to the input fets as well. so we should know how much (noise power) A&B will have and then refer it to the input and see the effects.
b)we should see the noise power at OPl & OPr and then refer it to the input.
which one above is correct?


i really appreciate any feedback!
 

baniliu

Junior Member level 1
Joined
Jan 11, 2007
Messages
19
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,373
Dear areboss,

Here let me try to give my idea about it.

1). kT/C will be the noise power integrated with the frequency range, for RC network, the noise produced by the resistor integrated to the high frequency detemined by 1/RC -3dB. But for a transistor, i don't think the kT/C is a proper description to the transistor noise power, it can be regards as the noise produced by the transistor integrate with its frequency range (the bandwidth is not only detemined by its intrinsic capacitance but often the external capacitance).

2.) It may be a comparator with latchly positive feedback with large gain, seems hard to get to a balance state. I think b) is reasonable, you also need to consider the load parasitic capacitance of the stage connected to OPI&OPR, that is the bandwidth of the sense amplifier.

baniliu
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top