Winfield Hill wrote:

Jeff wrote...

Needs to drive into 50 ohms. input level approx 150mV at 5Mhz

Winfield Hill wrote ...
Jeff wrote...

Ive been trying to locate a suitable unity gain buffer amplifier
IC that can drive a 50 load.
Application is to buffer a VCO output at 5Mhz.
Needs to be 8pin DIP

LTC's LT1206 comes in TO220, miniDIP and soic packages,
and Digi-Key has them in stock for $6.25 each...
http://rocky.digikey.com/WebLib/Line...ata/LT1206.pdf
http://www.digikey.com/scripts/DkSea...ail?Ref=329191

and operate on a single-ended supply.

Oops, +/-5V supply. What's your signal voltage? And did
you want your output to have a 50-ohm source impedance?

Unless you source with 50 ohms (2x signal plus 50-ohm resistor),
and terminate with 50-ohms, the issue becomes how much cable
capacitance? Either the load looks resistive (100 ohms in the
former case) or capacitive.


I would say it depends on the cable you choose. If there is a 50 Ohm load
and you connect it to your buffer amplifier with 50 Ohm coaxial cable, then
the buffer amplifier will see a 50 Ohm resistive load, not capacitive at
all.

It is probably still wise to use the gain-of-two amplifier and 50 Ohm source
resistor in case the load happens to be a poor match. If you really don't
need this feature then I would be tempted to use an emitter follower with
just one transistor. (Do they make transistors in DIP-8 packages?)

Chris