Stats

  • Locked Locked
  • Replies 4
  • Subscribers 125
  • Views 6238
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

How I can simulate input current noise in Chopper Amplifier using PSS+PNOISE analysis?

sahand1400

HI

I want to simulate a Chopper Amplifier, my circuit input source is current. The chopping frequency is 2.5k Hz, and the input signal frequency is 100 Hz.  I use virtuoso version 6.1.4 (IC6.1.4.485) for simulation.

 

I test two setups and have some question about setups. I don't know which one is correct.

 

First, can I use general current source without substitute it with PORT for chopper amplifier for pnoise simulation? (I test this state(fig1,fig2), but I expect the flicker noise is being reduced on the low frequency and noise will translate to clock frequency while the result shows some spikes near input frequency as shown in FIG 3. I am uncertain about noise data. Is it correct?

fig1

fig3

--------------------------------

Second, in another test-bench I use PORT+VCCS for pnoise analysis to measure the input referred noise current of chopper amplifier. I read a document on Pnoise simulation on mixer simulation in 

mixer simulation using spectre. In this tutorial, for pss+pnoise analysis all of the sources replaced with PORT. When I use PORT like the manual, I have to use VCCS to create current in circuit input. But when I do PSS+PNOISE analysis and plot the input noise using result ->direct plot the result is in V/sqrt(Hz), while I desired to plot the result in A/sqrt(Hz). In this state, since the PORT is in voltage the result for input noise is in is V/sqrt(Hz. I am not certain about PORT setting. In mixer manual the input port is DC and only clock port is signal. (I use sin voltage source in PORT)

I confused which one is correct. where I'm going wrong with the simulation setup? (In this case the result and setup are shown in fig 4)

fig4

best regard

sahand

  • sahand1400 said:
    I use virtuoso version 6.1.4 (IC6.1.4.485) for simulation.

    I may answer more over the weekend on the technical questions (it's late on a Friday for me), but my first question would be - why on earth are you using software from 11 or 12 years ago? It's not as if it's because you're stuck with an old CDB (IC5141) database - there absolutely no good reason to be using something this old.

  • in reply to Andrew Beckett

    Hi Andrew,

    Thanks for your reply. You are right. But I have to use this version because we are under sanctions and we do not have easy access to the latest version of this software. Any way I would be appreciate if you help me with these my minimal facilitate. My important question is which set-up is correct for a chopper circuit with current input to measure input noise using PSS+PNOISE?

    regards

  • in reply to sahand1400

    OK, I had a chance to read through this. First of all, there is absolutely no need to use a port component when using pss/pnoise. The only times you need to use a port are:

    1. When you are performing s-parameter analysis
    2. You are trying to represent a source with a power in an impedance-matched based system. For a voltage or current-based input there's no need
    3. You are measuring noise figure or noise factor - in that case you need a noisy input, and the resistance in the port generates noise.

    I'm not entirely sure what all those 100Hz sources are in the circuit, but I would expect that you do not need a time-varying signal source to measure the noise of your chopper amplifier. You'd need the clock for the chop to be defined, and you'd analyse over a period of that (I think that's 2.5KHz in your case). The actual signal input can be small-signal - the only time you might want a time-varying input to the amplifier is if the input is large and you want to investigate the intermodulation between the large signal input and the small-signal noise sources.

    Note that you will see peaks near the multiples of the PSS fundamental, because 1/f noise would be infinite at DC, and hence that will get mixed up to the multiples of the PSS fundamental - it's not really meaningful to measure the noise at exact multiples of the PSS fundamental anyway. If you didn't have the large-signal input to the amplifier, the fundamental would be 2.5KHz, and presumably you're only really interested in the noise in the band up to the Nyquist frequency?

    In the first circuit you seem to still have a port, but not sure where that is. Anyway, as I said there's no need to do that, and certainly no point having a port then a vacs to convert it back to a current source - that's completely unnecessary and a good way of both confusing yourself and increasing the likelihood of getting the wrong answer!

    Hope that helps,

    Andrew

  • in reply to Andrew Beckett

    Hi

    Thanks for your quick and helpful response.

    best regard

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.