The TIP120 in the Arduino basics example is a "up to 60V at 5A switch".
Would it be able to use in a simple circuit with 5V from the Arduino UNO to turn a LED on/off, or do I need a smaller transistor for that?
It will work, but the question is why you want to use it for a single led. The I/O pins can sink/source up to 40mA, and a signal led is usually set up at 20mA and less.
If you are simply trying to learn transistors, keep in mind that TIP120 is a darlington transistor IIRC. A simple bjt would do just fine
Yes I am simply trying to learn about transistors. But I can't seems to find any information of "recommended" transistors to begin with for simple Arduino projects.
I'm looking at BC557 (NPN) and BC547 (PNP) now. They are alot cheaper and I guess they'll do.
I was mostly afraid that the collector and emitter wouldn't be able to transfer between eachother if the circute voltage/power was just 5V.
Keep in mind, yes, pretty much everything has an upper voltage and current limit without damaging/destroying the component. They also give you a nice big current figure, but leave it up to you to figure out if the power dissipated in the device exceeds the junction temps. (heatsinks).
A BJT transistor is a CURRENT (I) controlled device. It relies on the current through the base to control the current through the collector/emitter. A base resistor is required to set the current to the base.
A mosfet is still a transistor, but a different variety. Basically, they are the latest and greatest of the transistors if you choose to think about it that way. They are VOLTAGE controlled devices. The 5V limitation of the arduino comes into play here. Any mosfet you use must have a RdsON of 5V or less or the thing won't work well. Don't fall into the trap of Vgs(th), that doesn't indicate the required voltage needed on the gate. Yes, there is different terminology- (G)ate, (S)ource, (D)rain. They are also called n or p channel vs the npn/pnp. I recommend sticking with n-channel first before delving into the p-ch variety.
Also understand the difference between low side / high side switching. It's easy enough to understand, but important if you want stuff to work right
I think any cheap transistor will work well for learning. Get any "general purpose" transistor and it cannot be wrong. Probably most interesting number is maximum current. Yours have "only" 200 mA. I have BC327/337 and they can switch nearly 1A.
tinman13kup:
The I/O pins can sink/source up to 40mA
I really would not advertise an absmax rating like that ...
If you google “ using a transistor as a switch “ there are some very good articles
If you google " using a transistor as a switch " there are some very good articles
Though some are bogus... so be warned.
For currents upto about 0.5A a small switching transistor like the 2N2222 is a useful choice - note
that the base current needs to be about 5 to 10% of the collector current for good switching (not
burning the transistor), which limits the use of a single BJT to about 0.5A from an Arduino pin
(which can only safely provide about 25mA reliably).
For larger currents a darlington pair (two transistors in one package) has a gain of 1000 for
switching, but loses 0.7 to 1.1V depending on device and load, so will get hot and might need a
heatsink, but can handle several amps if suitably cooled.
For both single BJTs and darlingtons you need to limit the base current with a resistor from the
arduino pin. 150 ohms is good for a single transistor, usually 1k is fine for any darlington.
For large currents a MOSFET is a simpler approach - choose a logic-level device (important),
with a low-enough on-resistance and you won't need a heatsink till you get to 10A or more
in practice. I-squared-R is the way to calculate the heat dissipation given the current and on-resistance,
try for less than 0.5W per device if you don't want to heatsink.