# Transistor question

Discussion in 'Electronic Basics' started by ngdbud, Dec 11, 2005.

2. ### Lord GarthGuest

The schematic is correct...

A positive voltage on the base will cause current to flow from the base to
the emitter
and into ground. When this happens, a large current will also flow from the
12 volt
supply through the coil and transistor and into ground.

Think about the circuit using conventional current, from + to - rather than
electron
flow.

PS. heat sink that 2N3055 very well!

3. ### Pooh BearGuest

Yes.

The collector is indeed positive wrt the emitter. See that " + " before the 12V ?

It would be conventional practice to say that the emitter is connected to ground and the positive suply
is connected to the collector load btw.

Graham

4. ### Paul BurridgeGuest

The little arrow in the symbol always points in the direction of
*conventional current flow* which is (historically) from positive to
negative. This is the opposite of electron flow, which is what we are
*really* concerned with. So the arrows in these symbols basically
point the 'wrong' way.

5. ### ngdbudGuest

Thnks, I have a small peltier cooler and a heat sink should use both?

P.S. the peltier is just a small 1.5v one, should i use a voltage
divider or is there some better way to divide the voltage by eight?

6. ### John PopelishGuest

Since a peltier is run on current, a series resistor is the simplest
way to regulate the current. But you will be wasting 7/8ths of the
power that way. A more efficient way (but a more complicated one)
would be to use a buck switching regulator, that converts power to
power. So, for example 8 volts @ .1 amp (.8 watt) in, would become
1.5 volts @ 5.333 amps out, minus switch and inductor losses. Losses
might be 10 to 20% of the output power. There are some integrated
circuits that do most of the work for this sort of thing. You just
add and inductor, a couple capacitors, and, perhaps a Schottky diode.

See simple switchers under switching regulators at:
http://www.national.com/catalog/0,4567,74,00.html

Here is a tutorial on buck switching regulators:
http://www.national.com/appinfo/power/files/f5.pdf

7. ### LacyGuest

As an aside from what Paul.has mentioned, You could also say that the arrow
always points to the N-material in semiconductors. This is especially
helpful when dealing with JFET or MOSFET devices when determining channel
type.This the way I learned it anyway. Thought this might be helpful to
know.