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How to connect BB signal from FPGA board to 50Ohm instrument input port

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rf1008

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Hello,all.

I need to connect my BB signal which has 100KHz frequency from FPGA board to signal generator at the EXT INPUT port, but i found the signal on FPGA board disappeared when the BNC cable is connected,and if i pull off the connector from signal generator, the BB signal is correct.
I think the issue is due to the unmatching between FPGA IO port and 50 Ohm signal generator. How to reslove it, thank you !
 

This is not mtaching/unmatching issue...
Your board can not drive 50 Ohm because of it's high output impedance.You should use a simple buffer amplifier for instance an OpAmp buffer etc..
 
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    rf1008

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BigBoss said:
This is not mtaching/unmatching issue...
Your board can not drive 50 Ohm because of it's high output impedance.You should use a simple buffer amplifier for instance an OpAmp buffer etc..
Click to expand...

Thanks!
Yes,I know this is not the matching/unmatching issue on impedance for mW or RF. Any other methods besides OPA buffer which needs PCB design.
 

Add a 450 (or 4950) Ohm resistor in series, so that you have a 500 Ohm (or 5kOhm) input impedance with 1:10 (or 1:100) voltage divider ratio.
 

rf1008 said:
Thanks!
Yes,I know this is not the matching/unmatching issue on impedance for mW or RF. Any other methods besides OPA buffer which needs PCB design.
Click to expand...
No, if the signal level is not very critical you may use series resistor solution proposed by volker but if there is a constraint on voltage level, you should absolutely buffer amplifier that can also be implemented on even on breadboard because of low frequency just to test it.
 

Thanks to you all.

Maybe,i have to use a buffer to resolve it. thanks.
 

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