Warning: DO NOT CONNECT TRANSISOTR DIRECTLY TO THE POWER! This movement might burn your circuit and cause hazard!
A transistor is a semiconductor device used to amplify or switch electrical signals and power. The transistor is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit.
There are two different types of transistors: bipolar junction transistor (BJT) and metal–oxide–semiconductor field-effect transistor (MOSFET). A BJT allows a small current injected at one of its terminals to control a much larger current flowing between the terminals, making the device capable of amplification or switching. While MOSFET has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. In other words, BJT use current to control the transistor resistance and MOSFET use voltage instead.
TIP 122 transistor
The TIP122 is a Darlington pair NPN BJT transistor, which is included in the kit. It functions like a normal NPN transistor, but since it has a Darlington pair inside it has a good collector current rating of about 5A and a gain of about 1000. It can also withstand about 100V across its Collector- Emitter hence can be used to drive heavy loads. The Darlington pair inside this transistor is shown clearly as its internal circuit schematic below. Read the TIP122 datasheet before you use it in the circuit.
The left pin of TIP 122 is the Base (B). which can turn ON or OFF the transistor. The middle pin is the Collector (C). Current flows in the transistor through collector. The right pin is the Emitter (E). Current flows out the transistor through emitter. Since transistor can be used as a switcher, it is dangerous to connect transistor directly to the power due to high current!
Some useful features of TIP 122 are:
- High DC Current Gain (hFE), typically 1000
- Continuous Collector current (IC) is 5A
- Collector-Emitter voltage (VCE) is 100 V
- Collector-Base voltage (VCB) is 100V
- Emitter Base Voltage (VBE) is 5V
- Base Current (IB) is 120mA