[time-nuts] Isolation achieved by opamp based isoamp?

Stephan Sandenbergh ssandenbergh at gmail.com
Fri Nov 22 04:45:43 EST 2013


Thanks for the spec. I suspected that it would be in that ball park.

The discrete transistor type amplifiers achieve around 120dB or more at
10MHz. But, they are a lot more effort to implement than the opamp designs.

I believe the transformer in this case is for ground loop isolation rather
than S12 isolation.


On 21 November 2013 20:20, Charles Steinmetz <csteinmetz at yandex.com> wrote:

> Corby wrote:
>
>  This opamp buffer has 80-90db isolation.
>>
>
> That is typical at 5 to 10 MHz *if* (i) all of the splitting is done on
> the input side (i.e., each output has its own op amp), and (ii) the
> splitter and all of the construction (grounds, shielding, etc.) is done
> correctly.
>
> If any splitting is done on the output side of the op amp(s), by using one
> op amp to drive more than one output through separate back terminating
> resistors, the outputs that share an op amp will only be isolated by 30 to
> maybe 40 dB (again, assuming that the op amp has been well chosen and all
> of the construction is done correctly).
>
> Best regards,
>
> Charles
>
>
>
>
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