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Comparison of CMOS and BJT

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isaacnewton

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ft bipolar vs cmos

Hello, everyone.

I am a graduate student in a univerversity. Most of our group members are doing BJT analog IC design. I don't know why my advisor sticks on the BJT. It looks like BJT tecknolog is going to die out. Searching the IEEE papers, there is no paper which is on BJT, most of them are on CMOS.

Is there anybody are also doing IC design on BJT? Does anybody know any companies are still using BJT tecknology?

And can somebody make a comparison on BJT and CMOS? Thank you.
 

cmos vs bjt

The reason MOS is a research topic is that it is newer. Bipolar was the earlier research topic and all of the ideas about it got used up. Bipolar is larger in die area and therefor not used in cost sensitive designs. It is much superior to MOS in many parameters and used where these are important.
 

Re: CMOS Vs. BJT

There are a lot of tehcnologies nowadays, some of them are GaAs and MMIC!

The reason why CMOS is still valueable because the capability to have a mix-mode design! SOC(system on chip) is also one of the reason as smaller and compact design is very important today!

BJT also have their own advantages, maybe your company is specialize on BJT design...You can set your own group to up-grade your company specialization on CMOS! I think it is better!! :D
 

Re: CMOS Vs. BJT

You can bet there are quite a few companies doing bipolar design. Bipolar is a valuable technology, especially when combined with CMOS i.e. BiCMOS - you can have the best of both worlds.CMOS is widely used because CMOS digital circuits are much better than bipolar in terms of area and static power consumption. And because people do SoC, then it is better if the analog part is done also in CMOS. Otherwise, bipolars have higher gm - about 10 times higher than MOS for the same current and also higher possible gain out of a stage. They are faster - higher Ft. They are better modeled, hence more predictable. On the downside - bipolars consume base current compared to no gate current for MOST (not quite true for 0.13u and 90nm technologies). Bipolars also occupy more area. Bipolar pnp are still quite worse compared to npn in terms of speed. The beta of bipolars is ill predicted - don't design based on this parameter.
 

Re: CMOS Vs. BJT

CMOS is mainstream technology because it is cheaper and easy to integrate analog part and digital part on the same die.
 

Re: CMOS Vs. BJT

yes .BJT is supirour in performance and it is used in critical designs and it is used in microwave amplifiers but "HBT"
and the BICMOS technologies is great so u can use CMOS devies an BJT and if the technology is SIGe u can have bipolar transistors with FT up to 100 to 200 GHz

so i geuss bipolar will be used
 

Re: CMOS Vs. BJT

In some universities, like UC Berkeley, the professors don't touch BJT when they teach Analog IC design.

Can somebody talk something about the future of CMOS and BJT? As the technology of CMOS improving, the BJT technology is going to die out?

Thank you in advance.
 

Re: CMOS Vs. BJT

isaacnewton said:
In some universities, like UC Berkeley, the professors don't touch BJT when they teach Analog IC design.

Can somebody talk something about the future of CMOS and BJT? As the technology of CMOS improving, the BJT technology is going to die out?

Thank you in advance.

We're using still BJT and CMOS together as BiCMOS and BJT never dies in
my opinion.

BJT is still superior than CMOS.

In next decade RFCMOS "may" be equivalent.But not now..
 

Re: CMOS Vs. BJT

To me it sounds strange that at Berkeley they don't teach bjt. After all Grey and Meyer book came out from there and was primarily about analog bipolar up to the 3rd edition and even also in the 4th.
 

Re: CMOS Vs. BJT

In general, MOS is noiser than BJT which is noiser than JFET.
 

Re: CMOS Vs. BJT

In my study here on subject Analog IC Design, my lecturer also didn't teach about BJT because we was concentarting on teaching CMOS technology. Why this is happen? As for me, if someone ask me to design circuit using BJT...I think I'll be lost! 8O

In my opinion, eventhough BJT is better than CMOS...a lot of study have being done to make sure CMOS technology can have a good performance as BJT technology!

:wink:
 

Re: CMOS Vs. BJT

simply coz the research in universities is industry driven so most of the universities concentrate in CMOS , coz most of the companies want to use this technology , coz it is much cheaper than BICMOS and GaAs technology

also most of the comerical products depends on CMOS

but if u want a very high performance like in military product u will not think how it will be cheaper but will need , very low noise devices and higher gain
so u will go to BICMOS and Bipolar and Jfets "GaAs"
 

Re: CMOS Vs. BJT

can have a look at the following doc....





sankudey
 

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