Re: 555 2n3055 was:The incredible inedible ignition coil

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

Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmnovak-at-msn-dot-com>

Jim,
What I like to do to put those 2n3055s into use is use a 555 to drive a
2n2222 and have it switch a current limited amount of the source into the
base of a 2n3055 on a seperate supply having a common ground. This way, the
2n3055 pretty much stays withinn it's ratings, doesn't get as hot, and
there's little chance of frying the 555 as a result of too much source
current being drawn. 2n3055s would not be my first choice for a power
transistor, but if i get a handful for free, they suddenly become my
favorite :þ

Cheers,

-Mike Novak



> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<jimlux-at-earthlink-dot-net>
>
> 555 can put out around 100 mA
> 2n3055 has a gain of about 10 at 5A collector current (meaning you'd have
to
> source 500 mA into the base)
>
> 3055's may be cheap, but they're not all that great a transistor: low
gain,
> low BVceo, awsome thermal runaway, etc..  There are many, many parts that
> are better and still under $1.