Switching mode transistor?

When a transistor works in swiching mode, does it have to work or switch between cutoff and triode region (the CMOS transistor is turned fully on and fully off)? Could it possibly switch between cutoff and triode region (the transistor is turned fulled off and just turned on, and using large transistor size can make Ron small so that it is still in triode region even if the input signal at the gate is small)?

Please see https://www.edaboard.com/threads/189659/

Of course, it can be switched between cutoff and satuation region.

leo_o2 said:

Of course, it can be switched between cutoff and satuation region.

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Really? The reason I am asking is that sometimes a transistor is meant to work in switch mode. Say, the transistor in output stage of a Class E power amplifier. It is meant to work/switch between cutoff and triode mode. That's why I think working bettween cutoff and triode mode is defined as switch mode. I haven't seen any application for switching between cutoff and saturation mode.

Another reason I ask is because I haven't got an answer for my question posted in the web link in my post above.

leo_o2 said:

Of course, it can be switched between cutoff and saturation region.

Click to expand...

If you switch a transistor between cutoff and saturation region, you always do this with another switch, which switches between cutoff and triode region (I call it "full switch"). Example: to switch on/off a constant current source from a current mirror (operates in saturation region), you either fully switch on/off its Vgs, or use a serial (cascoded) full switch.

BTW: Here's a nice English language exercise for pronouncing "switch":

Three swiss witchbitches, which wished to be switched swiss witchbitches, wish to watch three swiss Swatch watch switches. Which swiss witchbitch which wishes to be a switched swiss witchbitch, wishes to watch which swiss Swatch watch switch?

SCNR! ;-)

In IC, there are many cases for switching between off and satuation region. One of example is LED driver for very large screen.
In satuation region, it works in current regulation and transistor work in satuation region for most of cases. PWM switching is used to control LED dimming. As a result, LED brightness is controlled linearly.
I guess power amplifier can be controlled in the similar way.

sharethewell said:

Really? The reason I am asking is that sometimes a transistor is meant to work in switch mode. Say, the transistor in output stage of a Class E power amplifier. It is meant to work/switch between cutoff and triode mode. That's why I think working bettween cutoff and triode mode is defined as switch mode. I haven't seen any application for switching between cutoff and saturation mode.

Another reason I ask is because I haven't got an answer for my question posted in the web link in my post above.

Click to expand...

---------- Post added at 04:09 ---------- Previous post was at 03:58 ----------

For large current, controlling the power mos gate is usually used to turn off the current.
Two small transistors are needed.

erikl said:

If you switch a transistor between cutoff and saturation region, you always do this with another switch, which switches between cutoff and triode region (I call it "full switch"). Example: to switch on/off a constant current source from a current mirror (operates in saturation region), you either fully switch on/off its Vgs, or use a serial (cascoded) full switch.

BTW: Here's a nice English language exercise for pronouncing "switch":

Three swiss witchbitches, which wished to be switched swiss witchbitches, wish to watch three swiss Swatch watch switches. Which swiss witchbitch which wishes to be a switched swiss witchbitch, wishes to watch which swiss Swatch watch switch?

SCNR! ;-)

Click to expand...