Hi,

My company designs wideband active CTLE amplifiers used in high speed serdes channel application. I have an N5222A VNA and am wondering if I can measure the thermal noise output of this amplifier. I would like to then take this power spectral plot and integrate and calculate the RMS value and use this in signal integrity simulations assuming a Gaussian PDF. The amplifier I'm talking about has a 100Ohm differential 50Ohm single ended input and output impedance. I've seen some people use only KTB as the noise and some other use 4*R*KTB.

Any suggestions on how to do this properly or if possible on my VNA?

Thanks,

Ryan

Hi Ryan,

the answer is maybe. it depends on how much thermal noise your amplifier generates. You have a N5222A PNA, which has a couple of application options, option 028 (VNA standard receiver Noise Figure) and option 090 (spectrum analyzer). with these two measurements you can measure the excess noise coming out of your amplifier if you can overcome the noise figure of the VNA receiver, which is about 35 dB. So if your amplifier's gain+noise is greater than 35 dB, then you measure it's noise output with your PNA. if your amplifier alone can't overcome the VNA receiver noise figure, then you can add an LNA to VNA receiver path to lower the VNA receiver noise figure.

of course with our PNA-X line of VNAs (N524xx), we also have the option of a low noise receiver (option 029). We routinely use the option 029 to measure and calibrate the ENR of our own noise sources.