Part Number: OPA847
I want to use OPA847 as a gain block for a receiver between 50 to 500KHz.
I am using Keysight ADS with the workspace found on TI website, and simulating the noise figure using the spice model with ADS S parameter solver. How accurate are the results? Does anyone has a spreadsheet for calculation of noise figure from op amp noise parameters?
Jacob Freet High Speed Amplifiers
In reply to Jacob%20Freet:
There is an application note that gives equations for op amp noise figure.The title is Noise Analysis for High Speed Op Amps, and you can download it by searching on ti.com for the literature number: SBOA066A.
The app note gives an in-depth treatment of spot noise performance, and gives the detailed noise figure equations in section 7 - Computing Noise Figure.
Please review he app note and if it doesn't answer your questions let me know by replying to this thread.
In reply to John Miller - WEBENCH Design Center:
Please see attached spreadsheet, where I tried to follow example in section 8 in the application note. The numbers don't add up, please advise.
In addition could you please explain if my ADS noise figure simulations are accurate.
op amp noise figure.xlsx
In reply to Izik:
Please see he attached spreadsheet. The revs are shown in red font.It wasn't clear to me if you used an input termination resistor or not, so each case was added to the spreadsheet.The spreadsheet results are a little different than those in the app note, but they seem consistent with one-another.
Please note the OPA847 has a minimum stable gain of 12 V/V, which is greater than your chosen gain. This may matter when you compare the calculated and simulated noise results.
Regards,Johnop amp noise figure_revd.xlsx
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