a new method to simulate the noise?

[jake]

Hi all,
I find a way to simulate the noise in a circuit, the following is the method. But I measured the output voltage is zero. That is, there isn't noise in the circuit? I am puzzled by this. Who can tell me the reason? Thanks.
The method:
An adjunct to AC Analysis is the Noise Analysis. Here the AC source is turned off and the combined effect of all noise sources inside the circuit (resistors, currents) at the output is displayed.

Best regards
Jake

 

[mazelk]

A noise analysis is performed in conjunction with an AC sweep analysis and requires an .AC (AC analysis) command. When .NOISE is used, noise data is recorded in the Probe .DAT file for each frequency in the AC sweep.

The simulator computes:
• Device noise for every resistor and semiconductor in the circuit (propagated to a specified output node)
• Total input and output noise

At each frequency, each noise generator’s contribution is calculated and propagated to the output node. At that point, all the propagated noise values are RMS-summed to calculate the total output noise. The gain from the input source to the output voltage, the total output noise, and the equivalent input noise are all calculated.

(cite: OrCAD PSpice AD Reference Manual)

Besides, you must turn-on AC sources while noise calculating.

 

[jake]

A noise analysis is performed in conjunction with an AC sweep analysis and requires an .AC (AC analysis) command. When .NOISE is used, noise data is recorded in the Probe .DAT file for each frequency in the AC sweep.

The simulator computes:
• Device noise for every resistor and semiconductor in the circuit (propagated to a specified output node)
• Total input and output noise

At each frequency, each noise generator’s contribution is calculated and propagated to the output node. At that point, all the propagated noise values are RMS-summed to calculate the total output noise. The gain from the input source to the output voltage, the total output noise, and the equivalent input noise are all calculated.

(cite: OrCAD PSpice AD Reference Manual)

Besides, you must turn-on AC sources while noise calculating.

Mazelk, thank you very much! I get it.

 

[tia_design]

Here is a lab manual for noise analysis, hope helpful