Transistors

 The transistor is a semiconductor electronic element and is used to amplify electrical signals such as electronic switch, voltage stabilization, signal modulation, and many other applications. The basic element is many electronic circuits, integrated circuits and electronic computers. Transistors are divided into two main groups: bipolar transistor (BJT) and unipolar transistor (FET-Field Effect Transistor).

  History:

 The merits of the discovery of the transistor came to William Shockley in 1947. The first transistors were derived from germanium and the first silicon transistor was manufactured by Texas Instruments in 1954. The first unipolar transistor was manufactured in 1960.    

  Bipolar transistor(BJT)

 There are two types of bipolar transistors:

 · PNP (positive-negative-positive)

 · NPN (negative-positive-negative)  

    Contacts on bipolar transistors:

 · Base [B]

 · Emiter [E]

 · Collector [C]

 In conjunction with a common base, only the voltage amplification, in conjunction with the common collector, only amplifies the current and the connection with the common emitter increases the voltage and current, so the power gain is greatest.    

  Unipolar transistor (FET)

 They are characterized by their high input resistance and can be considered as a voltage-controlled active source. Unipolar transistors depending on the manufacturing technology can be:

 · Junction field-effect transistor (JFET)

 · Insulated gate FET (IGFET)

 · metal oxide semiconductor FET (MOSFET)

 · vertical metal oxide semiconductor FET (VMOSFET)

 Unipolar transistors can be n-channel or p-channel.     

   MOSFET     

   Gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (white) .

  When the switch is pressed the LED lights up. Mosfets need a pull down resistor due to the capacity of the gate. 

Transistor package:

 Small signal transistors: in small and medium power amplifiers and switching circuits:   

  Power Transistors: Manage large currents or high voltages:     

  RF transistors are designed to operate at very high frequencies: