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Ian Field

"Jan Panteltje" wrote in message
...
On a sunny day (Fri, 1 Feb 2013 11:13:45 -0800) it happened
(Dave Platt) wrote in :

In article ,
Jan Panteltje wrote:

Also how to tell you have a "digital" transistor in front of you?

WTF is a 'digital transistor'?????????????????

This is a fairly common term for a composite device... it's packaged
like an ordinary transistor (SMT or TO-92), but includes a
current-limiting resistor in the base lead (and often a base-to-
emitter pulldown).

It's used as a power-switching device, driven directly from a logic
signal (often a microcontroller pin).

Think of it as "just about the simplest sort of 'integrated circuit'
you can imagine". It's even simpler than the tiny little "simple glue
logic" chips you can buy these days (e.g. a NOT gate in a four-pin SMT
package, or a NAND in a 5-pin).

For a very short moment I did think 'unijunction transistor',
at least those are either on or off, but then I dismiossed that on
context.
I bought a bunch of 2n4246 UJTs last year from ebay.
Make nice oscillators.

I always preferred the programmable unijunction (a SS thyristor with the
gate on the anode instead of the cathode) - in fact you can turn the
standard relaxation oscillator upside down to suit a TO92 SS thyristor such
as 2N5061 MC100-4 etc - these SS SCRs are typically found in TV/monitor PSU
OVP shutdown latches.

Before Television Magazine went tits-up, I had a tester published with an
upside down relaxation oscillator to flash an LED (testing the SS SCR) and
also drive the IRLED in a high isolation opto-isolator that has no base pin
for the photo-transistor and can't be given the basic back-to-back diode
check.