Simulate input referred noise using Cadence noise analysis?

[w***@yahoo.com]

If I want to simulate input referred noise of an op amp using "Noise"
analysis in Analog Artist, is the configuration (unity-gain) below a
good way?
Vsin here is the independent source from analogLib. Since vsin itself
is noiseless, then all the noise should come from the amplifier itself,
in this case, onoise = input referred noise, right? Or Vsin can be
replaced with vdc with AC amplitude set to 0... ? Thank you for your
comments/corrections!

_________________
| |
| |
|________|\ |
| \ |
| \____|
________ |Amp/
| | /
| | /
(Vsin) |/
|
-------
---

[w***@yahoo.com]

Sorry, I meant AC magnitude "1".

Post by w***@yahoo.com
If I want to simulate input referred noise of an op amp using "Noise"
analysis in Analog Artist, is the configuration (unity-gain) below a
good way?
Vsin here is the independent source from analogLib. Since vsin itself
is noiseless, then all the noise should come from the amplifier itself,
in this case, onoise = input referred noise, right? Or Vsin can be
replaced with vdc with AC amplitude set to 0... ? Thank you for your
comments/corrections!
_________________
| |
| |
|________|\ |
| \ |
| \____|
________ |Amp/
| | /
| | /
(Vsin) |/
|
-------
---

[Andrew Beckett]

If you do a noise analysis, you can tell it where the input source is, and it
will then compute the input referred noise in whatever gain configuration
you've got. It's pretty silly measuring input referred noise in a different
conguration than you're actually going to use the amplifier.

You don't need to set an AC magnitude to do noise analysis - since it computes
the transfer function from the specified source to the output, and then
divides the output noise by that transfer function.

Regards,

Andrew.

Post by w***@yahoo.com
Sorry, I meant AC magnitude "1".

Post by w***@yahoo.com
If I want to simulate input referred noise of an op amp using "Noise"
analysis in Analog Artist, is the configuration (unity-gain) below a
good way?
Vsin here is the independent source from analogLib. Since vsin itself
is noiseless, then all the noise should come from the amplifier itself,
in this case, onoise = input referred noise, right? Or Vsin can be
replaced with vdc with AC amplitude set to 0... ? Thank you for your
comments/corrections!
_________________
| |
| |
|________|\ |
| \ |
| \____|
________ |Amp/
| | /
| | /
(Vsin) |/
|
-------
---

[w***@yahoo.com]

So putting a source there (vsin or whatever) is just to let the
simulator know where the input is? Did I understand this correctly?
Thank you very much!

[Andrew Beckett]

Post by w***@yahoo.com
So putting a source there (vsin or whatever) is just to let the
simulator know where the input is? Did I understand this correctly?
Thank you very much!

Yes, you need to have a current or voltage source (even if it is dc,
with zero-value), and then you need to indicate this source when you specify
the noise analysis. You're telling the noise analysis which source is the
input of the circuit.

Of course, if you don't care about input referred noise, you can tell it that
there isn't an input source.

Alternatively if you're computing noise figure or noise factor, you can tell
it that you have a port as the input (ports are like sources but have
impedance, and the impedance generates noise, which is important if you're
measuring noise figure - mostly for RF designers...)

Regards,

Andrew.