Re: solid state magnifier...accidentally...cool!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:

> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>

>         Won't work.  The driver feeds a high current through the primary and
> then interrupts it suddenly, producing an inductive voltage rise as the
> energy stored in the primary is released.  The OP AMP won't allow that
> rise.  I have found that, for 12 V power source and typical ignition
> coils, the voltage can go as high as three or four hundred volts.
> Usually use a shunt capacitor across the transistor to control the
> swing.  Value determined by careful "by guess and by gosh", usually of
> the order of 1 ufd or more.

The same idea used in classical induction coils. Without the capacitor
most of the energy is dissipated in the opening sparks at the primary 
interruptor.
In a solid-state induction coil, the capacitor can be used to limit
the voltage over the driving transistor, maybe allowing the use of
a low-voltage transistor as a 2N3055 in a safer way.

Antonio Carlos M. de Queiroz