Why Collector Is Lightly Doped?

Why is emitter always forward biased?

Emitter is always forward biased w.r.t base so as to supply majority charge carriers to the base..

Is VBE always 0.7 V?

VBE is the voltage that falls between the base and emitter of a bipolar junction transistor. VBE is approximately 0.7V for a silicon transistor. For a germanium transistor (which is more rare), VBE is approximately 0.3V. Again, this formula, can be used for either silicon or germanium transistors.

Why is the base of a transistor thin and lightly doped?

The base region in a transistor is made very thin so that there is a better conduction of majority carriers from emitter to collector through base. … The base region in a transistor is doped lightly so that the number density of majority carriers (electrons in p-n and holes in n-p-n transistor) is low.

Why is Collector current slightly less than emitter current?

The emitter current is always greater than the base current and the collector current. … The collector current is less than the emitter current because, a part of the emitter current consist of holes that do not contribute to the collector current.

Why emitter is highly doped?

The emitter is heavily doped, so that it can inject a large number of charge carriers (electrons or holes) into the base. The base is lightly doped and very thin, it passes most of the emitter injected charge carriers to the collector.

Which biasing method is the best?

Out of all these configurations voltage divider bias is the best, as the stability of this circuit with respect to change in beta, change in saturation current, change in base emitter voltage is more as compared to other configurations.

Which one is heavily doped?

In most transistors, emitter is heavily doped. Its job is to emit or inject electrons into the base. These bases are lightly doped and very thin, it passes most of the emitter-injected electrons on to the collector.

What is lightly doped?

Lightly Doped Drain. To minimize the hot carrier effect, the drain near the channel is doped less compared to the main drain area. This is called Lightly Doped Drain (LDD). To minimize the process complications, both source and drain are doped lightly near the channel region.

Why NPN transistor is preferred over PNP?

The majority charge carriers in an NPN transistor are electrons and the majority carriers in a PNP transistor are holes. The electrons have better mobility than holes. Therefore, NPN transistors are preferred over PNP transistors.

Is PNP or NPN more common?

PNP sensors tend to be more commonly used. Traditional relay type control circuit; Use with a programmable logic controller (PLC). … Less common nowadays are input cards that ‘source’, these were popular in Asia and require the NPN type of sensor in order to operate correctly.

What is a forward biased?

Forward bias or biasing is where the external voltage is delivered across the P-N junction diode. In a forward bias setup, the P-side of the diode is attached to the positive terminal and N-side is fixed to the negative side of the battery.

Which of the following is lightly doped?

Emitter is lightly doped, collector is heavily doped and base is moderately doped.

Which region is lightly doped in BJT?

The base region of a BJT transistor is very thin and is lightly doped with current carriers. It is the region of a transistor which has opposite polarity charge carriers from the emitter and the collector regions.

Can I use PNP instead of NPN?

Generally, the PNP transistor can replace NPN transistors in most electronic circuits, the only difference is the polarities of the voltages, and the directions of the current flow. PNP transistors can also be used as switching devices and an example of a PNP transistor switch is shown below.

Which is faster NPN or PNP?

A NPN transistor has electrons as majority charge carriers whereas the PNP transistor has holes as majority charge carrier. The mobility of electrons is better than mobility of holes. … mobility of electrons is more than hole,so as a result npn transistor are faster than pnp that’s why they are preferred..

Which is the least doped region in a transistor?

The base region is less doped as a result of those maximum current streams from the emitter to the collector, through the base. Less doping in base region lets less recombination of charges while moving from emitter to the base, therefore maximum charge carriers move towards the collector allowing Ic to be maximum.

Why is base lightly doped?

Why is the base of a transistor made thin and lightly doped?? The base is made thin and lightly doped so that the majority carriers supplied by the emitter do not combine in the base region and most of them pass on to the collector.

Why are collectors reverse biased?

The collector is kept at a higher potential than base or emitter so that the collector can attract all the electrons from emitter in case of a npn transistor as an example. For this to happen the collector base junction is reverse biased.