BJT is definitely faster than MOS....Please acknowledge....

what is scaling in bjt

BJT is faster:
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Ishan
Electronics & Telecomm Engineer

mos preferred than bipolar transistors

MOS was not faster earlier with BJT due to its MOS layer because its capacitance does not allow the input to be changing with very high frequency (due to charging and discharging).
Still it was preferred due to very very high input impedance and low power consumption.
But now we have comparable speed of MOS DEVICES with BJT.

bjt vs mos turn off

Ya MOSFET is mostly preffered because
firstly it is as faster as BJT due to advance fabrication technologies
2nd it requires less chip area than BJTs
hence it is easy to fabricate mos chips

is mosfet faster than bjt?

only due to scaling MOS has been able to reach the speed of BJT....

bjt speed

As said before, BJTs are faster than MOS as the parasitic capacitance in the MOS strongly affects the frequency response.

Why are MOS used in modern procesors??

That's due to scaling issues that are only applicable for MOS. Scaling down BJTs is a very hard process. Also BJTs consume more power than MOS.

A good proof that BJTs are faster is that scaling down MOS makes LOTS OF TROUBLE. e.g. high field, lower gm, verybad frequency response, etc...
On the other side, in most bipolar transistors the size of the device does not significantly affect the performance.
Even of that we use MOS as it is the only choice.

So, BJTs are faster

I've learned something which is
"Law of conservation of misery"
There is nothing perfect all the way.
MOS can't be small, fast and consume low power.
While BJTs are big, slow and consume high power.

There should be a trade off.

Sherif

MOS is definitely faster than BJT....Please acknowledge....

MOS is a majority carrier device, so it can achieve very high operating frequency. While BJT's speed is limited by the recombination of carriers at turn off. So MOS is faster.

Re: MOS is definitely faster than BJT....Please acknowledge.

yeechyan said:

MOS is a majority carrier device, so it can achieve very high operating frequency. While BJT's speed is limited by the recombination of carriers at turn off. So MOS is faster.

Click to expand...

well mosfet suffers the same problem... there is time needed for forming of channel...

Re: BJT is definitely faster than MOS....Please acknowledge.

As a rule, we should say BJT is faster than CMOS.... BUT it is not a complete rule, because nowadays there are some CMOS technologies that can rival with BJTs in speed !

Re: MOS is definitely faster than BJT....Please acknowledge.

yeechyan said:

MOS is a majority carrier device, so it can achieve very high operating frequency. While BJT's speed is limited by the recombination of carriers at turn off. So MOS is faster.

Click to expand...

It is specified in Gray Meyer that for a same technology BJT can have a larger transition frequency than MOSFET......