Electronics – Transistors


  • William B. Shockley (1910-1989)
  • Known as the Father of the Transistor
  • joined Bell Labs in 1936 in the vacuum tube department (solid state physicist)
  • Moved to the semiconductor laboratory: –It has today occurred to me that an amplifier using semiconductors rather than vacuum tubes is in principle possible. Invented  in 1944.


Transistor Type

Two different symbols are used for the transistor.




  • Functions in Analog
    • The transistor’s function is to amplify an electric current.
    • Many different kinds of transistors are used in analog circuits, for different reasons. This is not the case for digital circuits.
  • Functions in Digital
    • In a digital circuit, only two values matter; on or off.
    • The amplification ability of a transistor is not relevant in a digital circuit.
    • In many cases, a circuit is built with integrated circuits(ICs).
    • Transistors are often used in digital circuits as buffers to protect ICs.
    • For example, when powering an electromagnetic switch (called a ‘relay’), or when controlling a light emitting diode. (In my case.)



Water Analogy of transistors




Understanding Example One.

Understanding of Example Two



Understanding of Example Three


Understanding of Example Four




1st-letter 2nd –letter 3rd-
A=germanium A=diode Special or general purpose
B=silicon B=variable capacitance diode
C=gallium arsenide C=A. low power transistor (low power low frequency)
D=compound material (Ex Cadium sulphide) D=A.F low power transistor (high pass low frequency)
E=tunnel diode
F=H.F low power transistor (low pass high frequency
G=multiple device
H=magnetic sensitivity diode
K=hall-effect device
L=H.F power transistor (high pass high frequency)
M=hall-effect modulator
P=radiation resistive diode
Q=radiation generating diode
R=thyristor (SCR or triac)
S=Low power switching transistor
T=thyristor( power)
U=Power switching transistor
X= diode,multiplier
Y=power device
Z= Zener diode



  • BC547 –        general purpose low pass low frequency silicon transistor
  • ADF –        special purpose high pass low frequency germanium transistor
  • SL100 –        general purpose high pass high frequency silicon transistor
  • 2SAXXXX PNP type high frequency
  • 2SBXXXX PNP type low frequency
  • 2SCXXXX NPN type high frequency
  • 2SDXXXX NPN type low frequency






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