Buffer -- to 50Ohm PCB constraint - RF Cafe Forums
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Post subject: Buffer -- to 50Ohm PCB constraint Posted: Tue Jan 13, 2009 12:29 am
Joined: Thu Jan 08, 2009 10:27 pm
I have a buffer output (1MHz output at max) that needs to connect to a 50Ohm line (that runs the length of the PCB board)to be measured for frequency. There is about 6inches between the connector edge of this buffer output to the point where it meets up(becomes 50 ohms) on the PCB stripline.
At these low frequencies is it still worthwhile to establish the 50 ohm impedance closer to the connector or perhaps just using a low value series R close to the connector will suffice to mitigate reflections to the frequency counter?
Post subject: Posted: Thu Jan 15, 2009 6:56 am
Joined: Fri Feb 17, 2006 12:07 pm
Location: London UK
IMHO at such a low frequency anything goes, but to give peace of mind, you could insert a small T pad giving 6dB attenuation in a 50 ohm circuit, near the buffer output. I have often made these up from carbon film surface mount chip resistors; they give enough isolation against mismatches to avoid problems
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