115N. Small-signal model, MOS vs. BJT, core transistor behavior, transconductance

Analog Circuit Design (New 2019)
Professor Ali Hajimiri
California Institute of Technology (Caltech)
chic.caltech.ed...
© Copyright, Ali Hajimiri

[@MohammadAMaktoomi]

Dr. Hajimiri's response is excellent as to why people prefer mos over BJT (with notorious charge storage problem, base-collector schottky does help as in ECL, but at the expense of static power consumption). There are numerous other reasons but specifically, in this particular lecture, I would like to draw the audience's attention to fact that the designer has control over W/L ratio in case of MOS devices and just by changing it's W/L one can obtain more transconductance from a MOS transistor compared to the than a BJT (for the same of amount of bias current). In the case of BJT, the gm is the only function of the collector current.

[@Priyajit_Ghosh]

Sir, at 5:05, won't it be Ib+ Ic = Ie? You have written Ib+Ie = Ic

[@KipIngram]

38:30 - Why are we talking about BJT's? If you read Doug Self's "Small Signal Audio Design," he tells you point blank that you can't get the best distortion performance in your audio amps with MOFFETs. It's BJT all the way if you want the best possible fidelity. That's a *fantastic* book, by the way - I recommend it highly.

[@SmithKerona]

Yes BJTs are kings in audio design but most of modern analog integrated circuits are exclusively done in FETs specifically MOSFETs. This includes RF and Power Electronics. For example in RF you are not too concerned to get %0.0001 THD levels when amplifying signals. In fact it is common to see class C type RF amplifiers with insane levels of distortions. In these applications, MOSFETs are kings.

[@corydiehl764]

Is there a way to get access to the homework and problem sets? I'm really serious about mastering this material. Sounds like your problem sets are great for learning how to design and not just regurgitate.

[@boimax9963]

I would be really happy as well if we can get access to those!

[@hamzakourta4509]

I know it's been a long time but
did you find any?

[@corydiehl764]

@@hamzakourta4509 nope

[@hamzakourta4509]

@@corydiehl764 oh so sad 😢

[@anirudhnair558]

Amazing

[@seanpierre1338]

@Ali Hajimiri please go on Sean Carrolls podcast

[@homemade83]

why lessons numbers start at 101 ?
where the lessons before that ?
about what it was?
is it just related to the university code?

[@AliHajimiriChannel]

0XX lectures are from the undergraduate Circuits and System class and the 1XXN are from the Analog circuit Design class

[@priyamsaha]

5:02, I think there has been a mistake.

[@allthingsTechrelated]

Good stuff only problem I have is that the writing and drawings are so small that I cannot see some of them. Why trying to cram so much important stuff into a minute space. I’m using my reading glasses by the way.

[@beoptimistic5853]

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