Physics of p-n junction
Diode can be connected either in forward bias or reverse bias.But Diodes are coducting only in forward bias.i-e P region to positive terminal of the power supply and N region to negative terminal of the power supply.
If one side of a single crystal of pure semiconductor (Ge or Si) is doped with acceptor impurity atoms and the other side is doped with donor impurity atoms, a PN junction is formed. P region has a high concentration of holes and N region contains a large number of electrons.
As soon as the junction is formed, free electrons and holes cross through the junction by the process of diffusion.During this process, the electrons crossing the junction from N-region into the P region, recombine with holes in the P-region and holes from P region to N region recombine with electrons.Thus a region is formed, which does not have any mobile charges very close to the junction. This region is called depletion region.An electric field is set up, between the donor and acceptor ions in the depletion region.
The potential at the N-side is higher than the potential at P-side. Therefore electrons in the N-side are prevented to go to the lower potential of P-side. Similarly, holes in the P-side find themselves at a lower potential and are prevented to cross to the N-side. Thus, there is a barrier at the junction which opposes the movement of the majority charge carriers. The difference of potential from one side of the barrier to the other side is called potential barrier. The potential barrier is approximately 0.7V for a silicon PN junction and 0.3V for a germanium PN junction. The distance from one side of the barrier to the other side is called the width of the barrier, which depends upon the nature of the material.Diode can be connected either in forward bias or reverse bias.But Diodes are coducting only in forward bias.i-e P region to positive terminal of the power supply and N region to negative terminal of the power supply.
Diode as a circuit element – Clipping
Diodes are conducting only in forward bias. This property of diode is used in clipper ,clamper and rectification circuits.
when a diode is connected with an AC source ,then according to the bias diode will give only either a positive or negative peak of the AC voltage.A circuit which removes the peak of a waveform is known as a clipper.
Clamping
Rectification
Diodes are conducting only in forward bias. This property of diode is used in clipper ,clamper and rectification circuits.
when a diode is connected with an AC source ,then according to the bias diode will give only either a positive or negative peak of the AC voltage.A circuit which removes the peak of a waveform is known as a clipper.
Clamping
Rectification
Zener regulated power supply
OR, AND, NOT gates
Digital systems are constructed by using logic gates. The basic gates are the AND, OR, NOT gates. The basic operations are described below truth tables.
NAND , NOR and X -OR gate gates
NAND and NOR gates as building blocks
Transistor as a switch
Feedback amplifiers
Operational amplifiers and its applications – Inverting, non-inverting amplifiers
Digital systems are constructed by using logic gates. The basic gates are the AND, OR, NOT gates. The basic operations are described below truth tables.
NAND , NOR and X -OR gate gates
Transistor as a circuit element -
CC,CB and CE configuration
Feedback amplifiers
Operational amplifiers and its applications – Inverting, non-inverting amplifiers
– Adder – Subtractor – Integrator – Differentiator – Waveform generator – Comparator –
Schmidt trigger – Digital integrated circuits – Simple combinational circuits – Half and full adder – Flip-flop –Shift register –
Counters – Basic principles of A/D and D/A converters- Simple applications of A/D and D/A
converters – Microprocessor 8085: Architecture – Addressing modes – Instruction sets –
Simple programming.
