[time-nuts] Buffer / distribution amplifier for TCXO

[Bruce Griffiths]

Bruce Griffiths wrote:
>
> In which case a linear distribution amplifier is probably required.
>
> With only a ~3V supply available, options for the distribution 
> amplifier topology are somewhat limited.
> In principle you could use an emitter follower driving 4 other emitter 
> followers with a resistor in series with the emitters of the output 
> devices and the AC coupled loads to match the source to the 
> interconnecting cable impedance to minimise reflections without 
> requiring excessive dissipation in the emitter followers.
> With the low voltage supply available, using an RF choke is series 
> with the emitter follower's emitter to ground resistor will also be 
> useful in achieving the required dynamic range.
>
> Bruce

A more efficient buffer amplifier circuit schematic is attached.

The series transformer feedback stage has high input impedance and an 
output impedance matched to the transmission line (yes it works well 
with long transmission lines as well).
However a trifilar wound RF transformer is required.

In principle the various GPS receivers could be connected to taps along 
an end terminated transmission line using feedthrough connections with 
compensation for the tap shunt capacitance  if necessary.

A lower impedance line (eg 50 ohms) could also be driven at the expense 
of a higher collector current.
In this case the value of R3 would need to be reduced to around 100 ohms 
or so.

Bruce
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