. Basic building block of all microchips and even CPU.
. Developed by John Bardeen, Walter Brattaian and William Shockley in 1947.
. Made by semiconductor (conduct and insulate) devices like Germanium, Silicon etc.
. First computer had 2000 transistors, now powerful processors about 7 billion transistors
- Emitter
- Base
- Collector
. These three pins can be made of p-type or n-type semiconductors.
. Arrow mark shows the direction of current flow.
. One of the pins is common to both input and output forming 3 modes of configuration:
- Common Emitter mode
- Common Base mode
- Common Collector mode
. BJT's are suitable for low current applications.
. FET's are suitable for low voltage applications.
. In FET's instead of Emitter, Base and Current, it has Source, Drain and Gate.
. FET's are voltage controlled devices.
. Heating is less when compared to BJT's.
. In FET's only majority charge carries flows.
. Transistor can be used as switch.
. When input voltage is enough to drive transistor to ON, VCC flows to ground making output zero.
. When input voltage is low, transistor is OFF, it is open making VCC to flow to output and hence it is high.
. This concept is used to make LED bulb ON/OFF is most of applications like calculator, watches etc.
. When the circuit is designed as Amplifier using transistors, output is large compared to input.
. Developed by John Bardeen, Walter Brattaian and William Shockley in 1947.
. Made by semiconductor (conduct and insulate) devices like Germanium, Silicon etc.
. First computer had 2000 transistors, now powerful processors about 7 billion transistors
What it contains?
. It has three pins namely:- Emitter
- Base
- Collector
. These three pins can be made of p-type or n-type semiconductors.
. Arrow mark shows the direction of current flow.
. One of the pins is common to both input and output forming 3 modes of configuration:
- Common Emitter mode
- Common Base mode
- Common Collector mode
How it works?
. It works on fundamental of - ' Movement of electrons and holes between p-type and n-type semiconductors'.
. p-type means Group III element is added as impurity, n-type means Group V element is added as impurity to semiconductor.
. Speed at which computer perform calculations depend on transistor ON/OFF.
. p-type means Group III element is added as impurity, n-type means Group V element is added as impurity to semiconductor.
. Speed at which computer perform calculations depend on transistor ON/OFF.
. Faster the transistors, the faster computer works.
. It is what creates binary 0's and 1's that computer communicate and deal with Boolean logic.
. It replaced use of vacuum tubes.
Moore's Law: Number of transistors contained in IC doubles for every 18 months.
Types of Transistors:
. There are two types of Transistors called BJT (Bipolar Junction Transistor) and FET (Field Effect Transistor).. BJT's are suitable for low current applications.
. FET's are suitable for low voltage applications.
. In FET's instead of Emitter, Base and Current, it has Source, Drain and Gate.
1. p-n-p transistor:
. Base is made of n-type semiconductor.
. Emitter and Collector are made of p-type semiconductors.
. In p-n-p transistor, majority charge carriers are holes.
. Mobility of electrons is less, so less preferred.
. Mobility of electrons is less, so less preferred.
2. n-p-n transistor:
. Base is made of p-type semiconductor.
. Emitter and Collector are made of n-type semiconductors.
. In p-n-p transistor, majority charge carriers are electrons.
. It is mostly preferred because of higher mobility of electrons than holes.
. It is mostly preferred because of higher mobility of electrons than holes.
3. Field Effect Transistor:
. In many applications, FET's are mostly used rather than BJT's.. FET's are voltage controlled devices.
. Heating is less when compared to BJT's.
. In FET's only majority charge carries flows.
Applications of transistors:
. Transistors makes logic gates.
. These gates are used to make flip-flops .
. These are then used to make different building blocks like ALU, microchips etc.
. Transistor can be used as switch.
. When input voltage is enough to drive transistor to ON, VCC flows to ground making output zero.
. When input voltage is low, transistor is OFF, it is open making VCC to flow to output and hence it is high.
. This concept is used to make LED bulb ON/OFF is most of applications like calculator, watches etc.
. When the circuit is designed as Amplifier using transistors, output is large compared to input.
. This concept is used in amplifying sound signals in Microphones and feeding to loudspeakers.
