Bipolar Junction Transistor is a three terminal device. Whatever may be the use of a transistor either as an amplifier or as a switch it must have one input circuit and one output circuit. To facilitate the input and output circuit a transistor should have four terminals – two for input and two for output … Read more
There are different types of transistor available in the market, but for sake of understanding, we will consider a common emitter mode of NPN transistor. For this let us recall the basic structural features of npn bipolar junction transistor. Its emitter region is heavily doped and wider hence the number of free electrons (majority carriers) … Read more
A switch offers open circuit (infinite resistance) when it is put in ‘OFF’ position and offers short circuit (zero resistance) when it is put in ‘ON’ position. Similarly in a bipolar junction transistor, by controlling base-emitter current, the emitter-collector resistance can be made either nearly infinite or nearly zero. In a transistor characteristic, there are … Read more
Classification Based on Transistor Structure Point Contact Transistors These were the very-first Germanium transistors, which worked based on the basis of a difficult and unreliable electrical forming process, causing them fail quite often. Further, they had a common-base current gain α greater than 1 and exhibited negative resistance. Bipolar Junction Transistor (BJT) BJTs are the … Read more
History of Bipolar Junction Transistors The transistor (BJT) was not the first three terminal devices. Before transistors came into existence vacuum tubes were used. In electronics, vacuum tube triodes were used almost for half a century before the BJT’s. The light bulb invented by Thomas Edison in the early 1880’s was one of the first … Read more
Transistor Characteristics are the plots which represent the relationships between the current and the voltages of a transistor in a particular configuration. By considering the transistor configuration circuits to be analogous to two-port networks, they can be analyzed using the characteristic-curves which can be of the following types Input Characteristics: These describe the changes in … Read more
Mainly there are two types of transistors – Junction transistor Point transistor. Due to the small size and ruggedness, junction transistor is mainly used. They are of two types- PNP and NPN transistors (figure 1). These transistors are typically fabricated by means of five basic techniques as follows: Diffused Technique Point contact Technique Fused or … Read more
Triac is a three terminal AC switch which is different from the other silicon controlled rectifiers in the sense that it can conduct in both the directions that is whether the applied gate signal is positive or negative, it will conduct. Thus, this device can be used for AC systems as a switch. This is … Read more
Diac is a device which has two electrodes. It is a member of the thyristor family. It is mainly used in triggering of thyristor. The advantage of using this device is that it can be turned on or off simply by reducing the voltage level below its avalanche breakdown voltage. Also, it can be either … Read more
Transistors are one of the largely used semiconductor devices which are used for wide variety of applications including amplification and switching. However to achieve these functions satisfactorily, transistor has to be supplied with certain amount of current and/or voltage. The process of setting these conditions for a transistor circuit is referred to as Transistor Biasing. … Read more