[time-nuts] Looking for high reverse isolation amplifier

[John Miles]

> Great suggestion!  TI has eval boards available for them so I can
> get up to speed quickly.  I guess the idea is that I set it
> up for a gain of 2, and put a 50 ohm resistor in series with the
> output.  Now it is a unity gain buffer in a 50 ohm system.  A
> signal trying to go through it backwards has a source impedance
> of 100 ohms driving the output impedance of the amplifier, which
> is spec'ed at 30 milliohms, at least at low frequencies.  That
> works out to 70 dB, which is what you observed.  So
> I can see how it could have good reverse isolation.

Exactly, for unity gain you'd design for +6 dB and series-terminate the
output with 50R.   Good for capacitive loads as well as isolation.

> Do you run it in inverting or non-inverting configuration?

I've only used the non-inverting configuration (figure 1 from the
datasheet).  Takes about 20 minutes to dead-bug with 0603 resistors over
bare copper.

-- john, KE5FX
Miles Design LLC