>
> This one from Chris has an input stage similar to the design
> I did those years ago, but with added feedback and more.  
> The common base push-pull running open-loop, if memory serves,
> gave about 0.5 ohms input impedance running the devices at
> 100mA (on heat sinks !)
>

     Using the augmentation gives you a similar input impedance at far less 
current.  It gives you the opportunity to operate the transistor at it's best 
NF.

Chris