Hi Jan-Martin,

Doesn't seem like anyone has answered this--hope you're still
monitoring it for followups.

There was an article in the Nov 2001 "Electronics World" starting on
page 842, "Active RF Scope Probe," using a Maxim MAX4005. It's a
high-input-impedance unity-voltage-gain amplifier with a built-in 75
ohm source resistor. The probe design puts a little attenuation ahead
of that amplifier, probably mostly for protection in case you connect
to too large a voltage, and there's 6dB loss in the termination on the
far end of the transmission line; so the probe circuit adds a 10dB op
amp gain stage. I haven't read all the details but believe it's
designed for 100MHz bandwidth. He has it AC coupled, but it could
probably be DC coupled if you wanted.

Cheers,
Tom

"Jan-Martin Noeding, LA8AK" wrote in message . ..
Hi

need info about active high impedance buffer amplifier for RF probe,
believe Maxim makes such. Made a temporary circuit with discrete
components, it is shown as item #2.16 on my page
http://home.online.no/~la8ak/m2.htm
this is good enough for one purpose, but could well be used for RF
mV-meter covering larger range. If it is available from Linear
Technologies it would be even easier to obtain a sample

73

----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/