Hi
I found something called "logic level transistors" under mosfets on technobotsonline.com. Does this mean they are primarily used in switching? Am I wrong when saying this is perfect for pwm controlling a dc motor with a microcontroller or similar logic output?

 

More accurately, they're called "Logic level MOSFETs".

Very generally, such MOSFETs are considered fully ON when Vgs>=4.5v, where Vgs is the voltage on the gate using the source terminal as the reference.

You might use a uC to directly drive the gate of such a MOSFET for simple ON/OFF type control, or very low-frequency PWM. However, keep in mind that the drive capability of most uC's is limited to around 20mA, so that means you'll need to use a ~220 Ohm resistor between the uC's I/O pin and the gate of the MOSFET.

2N7000 N-ch MOSFETs come in a TO-92 package, and for practical purposes can sink up to 100mA.
A nifty MOSFET is the IRLD024; it comes in a 4-pin DIP package which makes it great for use with breadboards and protoboards. These are rated for up to 60v and 2.4A drain current, but a practical limit is 1.2A or less.

 

Thank you very much for your fullfilling answer!

 

We've come a long way from the first transistors I ever had, I somehow doubt anyone here is old enough to remember the 2N107, 2N170 and CK722. Those were your only choices as an experimenter in the early days and while I built a few circuits with them that actually worked the whole principle of current amplification was a mystery to me so I stuck with my trusty old vacuum tubes for years afterwards.

 

Yours had industry numbers? The first ones I saw were in metal tubes about the size of a 3/8" length of ballpoint refill tube. The leads were red, yellow, and blue - about 36 ga wire. They mounted in bitty nylon clips. Seymour Cray used them in the first Univac computers.

 

First I recall that were actually offered to the public as an experimenter's transistor. These allowed you to drive an actual speaker off your crystal radio set.