[volt-nuts] How to measure micro-amp currents and have low impedance?

[Bob Paddock]

On Sat, Sep 26, 2009 at 6:56 PM, Bruce Griffiths
<bruce.griffiths at xtra.co.nz> wrote:
> Use the Patterson transdiode connection with npn and pnp transistors as
> feedback elements.

I'm not familiar with Patterson's work, and Google was not much help.

Will you point me to a specific paper or schematic please?