How Can You Increase the Static Current Gain of a BJT?

[rclakmal]

static current gain of BJT?

to increase the static current gain of a BJT what should i do ?////////

1.base is made thin and heavily doped
2. collector is made thick and heavily doped
3.base is made thin and lightly doped
4.emitter is made thin and heavily doped

its an MCq question so i don't have any kind of pre works to show u hope that someone will help me with an answer with a valid reason.

 

[RajChakrabrty]

making thin and lightly doped base,
the recombination will be much less.
so,
amount of current coming from collector to emitter (or reverse),will be more and gain will be more.


*the main problem for currebt gain is recombination.
thin base means less area for recombination,
and
less doping also means so.

**for MCQ question,
this is the most likely factor,than others.

 

[phyzguy]

Actually, in today's bipolar transistors, the base is so thin that there is very little recombination. So the current gain is almost completely determined by the emitter efficiency. That is (for an NPN transistor) how much of the emitter current is composed of electrons injected from the emitter into the base , and how much is composed of holes injected from the base into the emitter. The higher the ratio of these two currents, the higher the gain. This ratio is determined by the ratio of emitter doping to base doping, so a heavily doped emitter and lightly doped base increases the current gain.

 

[RajChakrabrty]

Actually, in today's bipolar transistors, the base is so thin that there is very little recombination. So the current gain is almost completely determined by the emitter efficiency. That is (for an NPN transistor) how much of the emitter current is composed of electrons injected from the emitter into the base , and how much is composed of holes injected from the base into the emitter. The higher the ratio of these two currents, the higher the gain. This ratio is determined by the ratio of emitter doping to base doping, so a heavily doped emitter and lightly doped base increases the current gain.

this answer is really more practical and right than mine.

 

[DeeNos]

The static current gain of a BJT, also known as the DC current gain, is the ratio of the collector current (Ic) to the base current (Ib) in a BJT circuit. It is denoted by the symbol hFE or β. To increase the static current gain of a BJT, there are a few things that can be done:

1. Increase the doping concentration of the base region: By making the base region heavily doped, the diffusion current from the emitter to the collector will be increased, resulting in a higher collector current. This will lead to a higher value of hFE.

2. Increase the thickness of the collector region: A thicker collector region will have a larger area for current to flow, resulting in a higher collector current. This will also increase the value of hFE.

3. Decrease the thickness of the base region: A thinner base region will have a smaller area for current to flow, resulting in a lower base current. This will lead to a higher value of hFE.

4. Increase the doping concentration of the emitter region: By making the emitter region heavily doped, the diffusion current from the emitter to the base will be increased, resulting in a higher base current. This will also increase the value of hFE.

It is important to note that while these methods can increase the static current gain of a BJT, they may also have other effects on the performance of the transistor. It is important to carefully consider the trade-offs and choose the most appropriate method for the specific application.