Tejas Engineers Academy is conducting a free B.Tech Tuition Lecture. It will be based on details of BJT (Bipolar Junction transistor
Following is brief of Lecture:
Please note content of lecture is designed specifically for students seeking B.Tech Tuition from universities like IPU, MDU, UPTU, RTU, PTU, NSIT, DTU etc. If you are any student belonging to these universities having Analog Electronics subject then you can attend the series of B.Tech Tuition Lecture here at Tejas Engineers Academy.
Brief: – The transistor is a solid state device, whose operation depends upon the flow of electric charge carriers within the solid. Transistor is capable of amplification and in most respect it is analogous to a vacuum triode. The main difference between the two is that the transistor is a current controlled device whereas vacuum triode is a voltage controlled device. The transistor is only about six decade old, yet it is replacing vacuum tubes in almost all applications. The reasons are obviously its advantages over vacuum tubes such as compact size, light weight rugged construction, more resistive to shocks and vibrations, instantaneous operation, low operating voltage, high operating efficiency and long life with essentially no ageing effect if operated within permissible limits of temperature and frequency. However, transistors in comparison to vacuum triodes, have some drawbacks also such as loud hum noise, restricted operating temperature and operating frequency upto a few MHz. It
Till now we have discussed about basics of BJT. Analog electronics subject B.Tech coaching starts with the discussion of Biasing of BJT as follows.
For normal operation of transistor emitter base junction is always forward biased and collector base junction is always reverse biased.
For a moment if the biasing of emitter base junction is ignored and only collector base junction, which is reverse biased is considered then due to high resistance of reverse biased collector diode, practically no current would flow in the collector circuit.
Now if the biasing of collector base junction s ignored and only emitter base junction, which is forward biased is considered then practically whole of the emitter current flows through the base.
Till now we have covered details of biasing of BJT most important in the B.Tech Tuition of DTU student, because one question based on biasing of BJT is expected.
Important points to be remembered
1.Current conduction in npn transistor is by electrons and the conventional current flow will be in the opposite direction. Current conduction in pnp transistor is by holes but in external leads, the current conduction will be by flow of electrons.
2. The collector current IC is always less than emitter current IE being the difference of emitter current and base current.
Above two points are very important keeping in view of B.Tech coaching for Analog electronics for IPU examinations.
3. The base current is only a small fraction of emitter current
4. Emitter base junction is always forward biased and collector base junction is always reverse biased for active region of operation.
5. Transistor transfers the input signal from a low resistance circuit to a high resistance circuit, therefore it is called the trans-istor
