Advertisements
Advertisements
प्रश्न
With the help of a neat diagram, explain the working of the npn transistor?
Advertisements
उत्तर
Working of n-p-n transistor:
- The majority of charge carriers in the emitter of the n-p-n transistor are electrons.
- A typical biasing of a transistor is shown in figure (a). In this, the emitter-base junction is forward biased while the collector-base junction is reverse biased.
Figure (a) - At the instant when the EB junction is forward biased, electrons in the emitter region have not entered the base region as shown in figure (b).
Figure (b) - When the biasing voltage VBE is greater than the barrier potential (0.6 – 0.7 V for Si transistors), many electrons enter the base region and form the emitter current IE as shown in figure (c).
Figure (c) - These electrons can either flow through the base circuit and constitute the base current (IB), or they can also flow through the collector circuit and contribute towards the collector current (IC).
- The base is thin and lightly doped, the base current is only 5% of IE.
- Electrons injected from the emitter into the base diffuse into the collector-base depletion region due to the thin base region. When the electrons enter the collector-base depletion region, they are pushed into the collector region by the electric field at the collector-base depletion region. The collector current (IC) flows through the external circuit as shown in figure (d). The collector's current IC is about 95% of IE.
Figure (d)
From the figure, we can conclude that IE = IB + IC Since the base current IB is very small we can write IC ≈ IE.
APPEARS IN
संबंधित प्रश्न
Why is the base of a transistor made thin and is lightly doped?
In a common-base connection, a certain transistor has an emitter current of 10mA and a collector current of 9.8 mA. Calculate the value of the base current.
Which method of biasing is used for operating a transistor as an amplifier?
In a common base configuration, the transistor has an emitter current of 10 mA and a collector current of 9.8 mA. The value of base current is ______
The light emitted in an LED is due to
Explain the need for a feedback circuit in a transistor oscillator.
Transistor functions as a switch. Explain.
In the circuit shown in the figure, the BJT has a current gain (β) of 50. For an emitter-base voltage VEB = 600 mV, calculate the emitter-collector voltage VEC (in volts).
For a transistor, the current ratio 'βdc' is defined as the ratio of ______.
In the symbol for a transistor, the arrow head points in the direction of the ____________.
Least doped region in a transistor ____________.
In switching circuit, transistor is in ON state. Values of IC and IB are 5.2 mA and 10 µA respectively and value of RC is 1 k`Omega`. If Vcc is at 5.5 V, then VCE is ______.
Ve, Vb, and Ve are emitter, base, and collector voltage respectively for npn transistor in CE mode. Amplifier works for the combination of biasing voltage equal to ______.
ln switching circuit, transistor is in ON state and values of IC and IB are 4.2 mA and 5 µA respectively and RC= l k`Omega` and RB= 300 k`Omega`. If VBE = 0.5 V, find the value of VBB.
In a transistor in CE configuration, the ratio of power gain to voltage gain is ____________.
In switching circuit, transistor is in ON state, values of IE and lB are 10 mA and 0.8 mA respectively and RL is 2 k`Omega`. If VCE is 7.6 V, then VCC is ____________.
For a common emitter configuration, if 'α' and 'β' have their usual meanings, the correct relationship between 'α' and 'β' is ______.
In a silicon transistor, a change of 7.89 mA in the emitter current if produces a change of 7.8 mA in the collector current, then the base current must change by ____________.
In a transistor, the thickness of the base region ____________.
For an ideal diode, the current in the following arrangement is ______.
A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 2000Ω. The power gain of the amplifier is ______.
A transistor is used as a common emitter amplifier with a load resistance 2 KΩ. The input resistance is 150 Ω. Base current is changed by 20 µA which results in a change in collector current by 1.5 mA. The voltage gain of the amplifier is ______.
The base current in common emitter mode of the transistor changes by 10 µA. If the current gain of the transistor is 50, then change in collector current is ______.
The transfer ratio of a transistor is 50. The input resistance of the transistor when used in the CE configuration is 1K Ω. The peak value for an AC input voltage of 0.01 V of collector current is ______.
Explain the working of the n-p-n transistor in a common base configuration.
