Relation between the current gain of common base and common emitter amplifier.
β = α / 1 – α = I c / I e
The input and output signals are out of phase by π or 180 ° There is amplification in current, voltage and power of the given signal.
Light Emitting Diodes( LED)
It is forward biased p-ri junction diode which emits light when recombination of electrons and holes takes place at the junction.
If the semiconducting material of p-ri junction is transparent to light, the light is emitting and the junction becomes a light source, i. e., Light Emitting Diode( LED).
The colour of the light depends upon the types of material used in making the semiconductor diode.
( i) Gallium – Arsenide( Ga-As) – Infrared radiation
( ii) Gallium – phosphide( GaP) – Red or green light
( iii) Gallium – Arsenide – phosphide( GaAsP) – Red or yellow light
Logic Gate
A digital circuit which allows a signal to pass through it, only when few logical relations are satisfied, is called a logic gate.
Truth Table