semiconductor Transistors

Transistors are semiconductor devices for controlling current flow. A "transistor" (transformer + resistor) transfers signals across the resistance of two semiconductor materials. 
1 - TYPES / USES
There are many types of transistors.

• Bipolar transistors are most common for switching and amplifying.
  
• Field-effect transistors (FETs) are quite different. They are used as switches, amplifiers, and voltage controlled resistors.


• Power transistors are a variation for larger currents; exposed metal carries away heat.


• Phototransistors are another variation, used as light-sensitive switches in speedometer and headlamp systems.

2 - SYMBOLS

• Bipolar transistors are shown with a line and arrow for the emitter, a heavy T-shaped line for the base, and a line without an arrow for the collector.
  The emitter arrow points to the negative side of the circuit.


• Phototransistors have incoming light arrows added.


• FETs have an arrow showing negative (N) or positive (P) voltage.

3 - OPERATION
In bipolar transistors, a small base current (Ib) between the emitter-base "turns on" the transistor and causes a larger current (Ic) to flow between the emitter-collector. In phototransistors, light striking the base "turns on" the transistor. This switches on a second transistor which amplifies the signal.

AutoHex II

Autohex II For BMW

AutoHex II For Kia and Hyundai

AutoHex stand alone

Mercedes Technical Info