On 6 March 2015 at 16:13, Robert Dvoracek <lgtngstk@hotmail.com> wrote:

> This reminds me of the zener booster circuit.
> I have no idea how this works.
>
> http://www.dissident-audio.com/Yves/Z-Booster.gif


In both cases, the transistor turns on when Vin starts to exceed Vzener +
transistor turn on voltage.

This is intended to increase the available power dissipation compared to
using zenera alone BUT is liable to make the turn on kneww even softer than
from th zener alone.

The threshold is also poorly defined.

The bjt turns on at nominally 0.6V but has some significant conduction at
Vbe =3D 0.5V


The MOSFET has a Gdsth turn on voltage where it draws a defined Ids at a
defined Vds - the latter may be > Vzener depending on the application so
getting a well defined result is hard and/or unlikely. In both cases,
reducing the size of the resistor to ground will 'stiffen things up'.



Russell
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