[aerlinger]

This video covers a particular type of transistor known as the Bipolar Junction Transistors (BJTs). These are more commonly used in analog applications like amplification and signal processing rather than digital logic (though they can be used in specialized digital logic circuits).

Today, field effect transistors (FETs) reign supreme for most IC applications such as CPUs and digital logic as they're more scalable and efficient than BJTs and have a very different structural design.

[marshray]

BJT's are also still used for some very high-power applications because they can be more efficient at very high currents.

In fact, they invented a new part that has the "input" gate of an FET and the Collector-Emitter "output" of a BJT!

https://en.wikipedia.org/wiki/Insulated-gate_bipolar_transis...

[baybal2]

> In fact, they invented a new part that has the "input" gate of an FET and the Collector-Emitter "output" of a BJT!

IGBTs are far from being a new invention.

And if we are speaking strictly, very high currents aren't switched with higher net efficiency by BJT than FET.

The reason SCR type devices are used for the kiloamperes range switches is due to them being the only switches which can mechanically/thermally handle so much current.

But for high voltages, bipolars will indeed go higher than FETs.

[marshray]

In "on" mode, FETs appear as a small resistance R_ds_on, but BJTs act like a mostly-constant voltage drop V_ce_sat.

So for any BJT and FET we compare, passing a current less than V_ce_sat/R_ds_on is more efficient on the FET, and for greater currents the BJT is more efficient.

[baybal2]

> for greater currents the BJT is more efficient

Depending on voltage. Extremely low RDs ON FETs are there. The real world choice would depend on whether you just need a constantly open switch, or high frequency switching for power conversion.

Are you in power electronics?

[FunkyDuckk]

FETs are also more common for many analog applications.

[exmadscientist]

FETs and BJTs are both common for analog. Discrete analog tends to prefer BJTs, which (among other features) have much higher transconductance, which you can never get enough of. FETs offer ultra-high input impedance, better performance at low power (though BJTs ain't all bad there), and the big one... they're built on CMOS processes. That means you can integrate your analog stuff with a giant pile of digital logic, which is a tremendously useful thing to do. (But the analog section alone often would be better if it were on a bipolar process.) Op-amps are split evenly between both types. Okay, evenly-ish.

[lawrenceyan]

And FinFETs are state of the art currently for semiconductor applications.

[adgjlsfhk1]

technically gate all around is sota, but not yet in production

[lawrenceyan]

Thanks! I try my best to stay up to date, but haven't looked much into this. This is super cool.

[commandlinefan]

Any videos on how FET's work?

[spullara]

https://www.youtube.com/watch?v=c-3p8moNXfI