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Simulators >> Circuit Simulators >> a question about circuit noise
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Message started by youchen on Jun 13^th, 2008, 1:14pm

Title: a question about circuit noise
Post by youchen on Jun 13^th, 2008, 1:14pm

Hi, it is my understanding that the general transient analysis in SPICE or SPECTRE does not take into consideration of the random device noise, such as the thermal noise, shot noise, flicker noise etc. Is this right? If it is, so this means that the SNR obtained from transient simulation for A/D converters is the nominal SNR with quantization noise and other deterministic noise only?

So, how do we take into consideration of random device noise for general circuits, like OpAmps or even timing delay of digital circuits ? If there are 100 transistors in the circuit, how can the random noise for each transistor be considered in the transient simulation? Thank you for your help.

Title: Re: a question about circuit noise
Post by thechopper on Jun 13^th, 2008, 2:53pm

Hi Youchen,

You are correct: general transient analysis does not consider random device noise. In order to consider it you should run a transient noise analysis. This analysis generates the random device noise of any component in your circuit and superimposes it on any signal that you apply to it. This is available in SPECTRE as far as I know.

Regards
Tosei

Title: Re: a question about circuit noise
Post by Ken Kundert on Jun 13^th, 2008, 11:18pm

Generally the small signal noise analyses (noise or pnoise) are preferred over transient noise. You would use noise for the opamp and pnoise for the logic circuit.

-Ken