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

questions on current noise simulation

Status
Not open for further replies.
H

hyleeinhit

Member level 3
Joined
Aug 11, 2008
Messages
58
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Location
U.S.
Activity points
1,696
Hi, guyes,

I ran into problem when I simulate input inferred equivalent noise with AMI 0.5um CMOS process with cadence spectre. I followed noise analysis note in https://www.ece.tamu.edu/~spalermo/ecen474/noise_sim_notes.pdf and set the flicker noise simulation parameters:

[For NMOS model, add the following to the end of your model :
KF=0.276E-25 &
AF=1.53 &
)
For PMOS model, add the following to the end of your model :
KF=0.466E-26 &
AF=1.61]

In noise analysis, I set iprobe3 as output and Iin as input current source. Iin DC value is set at 10nA for DC bias; Iin AC magnitude is set at 1 for noise simulation.
To display the input referred current noise, I selected RESULT->DIRECT PLOT->EQUIVALENT INPUT NOISE. However, I got quite strange input referred current noise result: Noise in high freq. domain is higher than that in low freq. domain. In theory, should low freq noise be higher than high freq noise because of flicker noise?
Anyone can help me out?
 

Attachments

  • schematic.JPG
    schematic.JPG
    146.7 KB · Views: 96
  • noise simulation result.JPG
    noise simulation result.JPG
    96.9 KB · Views: 123
Last edited:

I got quite strange input referred current noise result. Noise in high freq. domain is higher than that in low freq.
Click to expand...
What's strange with this result? Any MOSFET has it, review your text books. Gate capacitance converts voltage noise into current noise.
 

what is the transfer function of the circuit? Is it working correctly? Input referred noise can look unusual sometimes as it is taken by applying the input-output transfer function to the output noise in reverse. If the frequency response of the system is unusual then the output noise can look sensible but input referred can look strange.

Keith
 

FvM said:
What's strange with this result? Any MOSFET has it, review your text books. Gate capacitance converts voltage noise into current noise.
Click to expand...

Because of flicker noise, should low freq noise be higher than high freq noise?

- - - Updated - - -

keith1200rs said:
what is the transfer function of the circuit? Is it working correctly? Input referred noise can look unusual sometimes as it is taken by applying the input-output transfer function to the output noise in reverse. If the frequency response of the system is unusual then the output noise can look sensible but input referred can look strange.

Keith
Click to expand...


Sound reasonable.

Is there any problem in my noise analysis setting?
 

Because of flicker noise, should low freq noise be higher than high freq noise?
Click to expand...
Voltage noise yes, current noise no. See a typical MOSFET noise characteristic:

 
FvM said:
Voltage noise yes, current noise no. See a typical MOSFET noise characteristic:

Click to expand...

Thanks. I understand it a little bit. Define input referred voltage noise as Vnin, and input capacitance as Cin, input referred current as Inin.

Inin=Vnin*j*w*Cin

Thus, high freq Inin component is larger than low freq Inin component.

BTW, I find a different image about input referred noise plot from

https://www.planetanalog.com/document.asp?doc_id=528133

. Any comments?

c0694-figure2.gif
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top