What is a Transistor? • A Transistor is an electronic device • composed of layers of a semiconductor • material which regulates current or • voltage flow and acts as a switch or gate • for electronic circuit.
History of the Transistor • John Pierce –supervised the Bell Labs team which built the first transistor (1947) • First Solid State Transistor – (1951) Gordon K. Teal (left) and Morgan Sparks at Bell Laboratories, 1951 • Akio Morita, who founded a new company named Sony Electronics that mass-produced tiny transistorized radios (1961)
Applications • Switching • Amplification • Oscillating Circuits • Sensors
Composed of N and P-type Semiconductors • N-type Semiconductor has an excess of electrons • – Doped with impurity with more valence electrons than silicon P-type Semiconductor has a deficit of electrons (Holes) • – Doped with impurity with less valence electrons than silicon
P-N Junction (Basic diode): • - Bringing P and N Semiconductors in contact • P Type N Type • - Creation of a Depletion Zone
Reverse Biased => No Current Forward Biased => Current • Applying –Voltage to Anode increases • Barrier Voltage & Inhibits Current Flow • • Applying Voltage to Cathode • Barrier Voltage to Anode allows current flow
Types Of Transistors NPN: transistor where the majority current carriers are electrons The majority current carriers in the PNP transistor are holes