Electronic

Smoothing In the circuit above, the `one-way’ direct current flows in a series of surges with brief periods of zero current in between.  These surges can be partly smoothed out by connecting a large capacitor across the load. The capacitor charges up when current flows from the diode, then discharge through the load when the … Read more

Full-wave Rectification The figure above shows a circuit to produce full-wave rectification.  Using an ingenious arrangement of diodes, called a bridge rectifier, this reverses the negative half of each a.c. cycle, instead of just blocking it.  The result is that current always flows in the same direction through the load, no matter which way it … Read more

Half-wave Rectification Diodes are also known as rectifiers. They can be used to change a.c. into d.c., a process called rectification. A simple rectification circuit is shown in the figure below. The final waveform on the screen is the positive half only of the original a.c. waveform – hence the term ‘half-wave’ rectification. Half-wave rectification: … Read more

Forward Bias And Reverse Bias (figure 1) The figure above shows a dc source across a diode. The negative source terminal is connected to the n-type material, and the positive terminal is connected to the p-type material.  This connection Figure is called forward bias. Current flows easily in a forward-biased silicon diode. (Figure 2) Turn … Read more

The p-n junction We can produce a single crystal with a p-type semiconductor on one side and n-type on the other side as shown in the figure above. The border where the p-type and the n-type region meet is called the p-n junction. Depletion Layer and Junction Voltage At the p-n junction, electrons from the … Read more

p-type semiconductor n-type semiconductor Doping Material Trivalent:aluminium, boron, and gallium Pentavalent:antimony, and phosphorus Role of doping material Atom receiver Atom donor Majority Charge Carrier Holes Free electrons Minority Charge Carrier Free electrons Holes

n-type Semiconductor A p-type semiconductor can be produced by doped some trivalent atoms into a semiconductor. Trivalent atom is atom has only three valence electrons. Examples include aluminium, boron, and gallium. The figure above shows an aluminium atom (which is trivalent ) in the centre, surrounded by four silicon atoms. We can see that, the trivalent … Read more

n-type Semiconductor The n-type semiconductor can be produced by doped some pentavalent atoms into a semiconductor. Pentavalent atoms are atoms that have 5 electrons in the valence shell. Examples of pentavalent atoms include antimony and phosphorus. The figure above shows how the silicon crystal appears after doped with a phosphorous atom, which is pentavalent. We … Read more

Doping A Semiconductor One way to increase the conductivity of a semiconductor is by doping.  Doping is a process of adding a small number of impurities to a semiconductor. The impurities added to the semiconductor are called dopants. By adding impurity atoms to a conductor can increase its electrical conductivity.  There are two types of … Read more

Flows of Free Electrons and Holes We have learned that there are 2 types of charge carrier in a semiconductor, the free electrons and the holes. The free electrons carry negative charge whereas the holes carry positive charge. If a potential difference is applied to a semiconductor, the electrons and holes will start to flow. … Read more