pn junction diode, rectifiers with and with out filters
- 1. INSULATORS/CONDUCTORS • Materials that have large bandgap energies (in the range of 3 to 6 electron- volts (eV)) are insulators, because at room temperature, essentially no free electron exists in the material • Materials that contain very large number of free electrons at room temperature are conductors
- 2. SEMICONDUCTORS • In a semiconductor, the bandgap energy is in the order of 1 eV. The net flow of free electrons causes a current. • In a semiconductor, two types of charged particles contribute to the current: the negatively charged electrons and the positively charged holes
- 3. MOVEMENT OF HOLES A two- dimensional representation of the silicon crystal showing the movement of the positively charged hole
- 4. EXTRINSIC SEMICONDUCTORS / DOPING • The phosphorus (group V) atom is called donor impurity because it donates an electron that is free to move • The boron (group III) has accepted a valence electron (or donated a hole), it is therefore sailed acceptor impurity
- 5. N – TYPE SEMICONDUCTOR Two-dimensional representation of a silicon lattice doped with a phosphorus atom
- 6. P – TYPE SEMICONDUCTOR Two-dimensional representation of a silicon lattice doped with a boron atom
- 8. P-N JUNCTION FORMATION • Electrons and holes remain staying close to the p-n junction because negative and positive charges attract each other. •Negative charge stops electrons from further diffusion •Positive chaige stops holes from further dilfusion •The diffusion forms a dipole charge layer at the p-n junction interface. •There is a “built-in” VOLTAGE at the p-n junction interface that prevents penetration of electrons into the p-side and holes into the n-side.
- 9. Diode Circuit Symbois N material (cathode) Reverse Bias P material (anode) Forward Bias
- 10. When “plus” is applied to the p- side, the current is high. This voltage polarity is called FORWARD. When “plus” is applied to the n-side, the current is nearly zero. This voltage polarity is called REVERSE. P- N Diode Circuit Notation
- 11. T diode i-v relatioaship with s•rm scales cxps‹sted and others compressed in order la reveal deteJI«. The experimental I-V characteristic of a Si diode
- 12. 'Z • A Zener is a diode operated in reverse bias at the Peak Inverse Voltage (PIV) called the Zener Voltage (VZ). • Common Zener Voltages: 1.8V to 200V (a) ZENER DIODE
- 14. RECTIFICATION • Conversion of ac to pulse setting dc • Full-Wave Rectification: Rectifies both halves of the AC waveform. • Half-Wave Rectification: Rectifies only one half of the AC waveform.
- 17. FILTERS • We have now used diodes to produced a pulsed dc signal. • Most equipment requires “regulated” dc — We must remove the “ripple” — Ripple is departure of waveform from pure dc (!Iat, constant voltage level) • Frequency — so far we have seen pulsed dc at the same frequency as the input (1/2 wave) or twice the line frequency (full wave rectifier) • Amplitude — a measure of the effectiveness of the filter
- 18. FULL WAVE CAPACITIVE FILTER
- 19. FULL WAVE RECTIFIER CIRCUIT WITH INDUCTOR FILTER