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Field Effect Transistor, a transistor in which most current is carried along a channel whose effective resistance can be controlled by a transverse electric field. Commonly used types of FETs include the Metal Oxide Semiconductor FET (MOSFET), and less common in recent designs, the Junction Gate FET (JFET or JuGFET).

3 votes

Puzzled by FET circuit

Ignoring that spurious extra ground at the top right (presumably supposed to go to the microcontroller GPIO), the JFETs will present a low impedance near 0V and increase for (poorly controlled) higher …
Spehro 'speff' Pefhany's user avatar
12 votes

Why would you use a shared-gate multi-channel MOSFET device?

The manufacturer says it is useful in "smart phones" and as a "load switch". The lack of any matching specifications would tend to indicate it's intended for switching only. Maybe a low-side switch fo …
Spehro 'speff' Pefhany's user avatar
12 votes

Why (not) put a resistor on FET gate?

Edit: Re-interpreting the value shown on the datasheet. The resistance shown is not M\$\Omega\$, much lower, more like 3400 ohms based on the change in the switching times with external gate resistor. …
Spehro 'speff' Pefhany's user avatar
5 votes
Accepted

FET-based voltage regulator with TL431

This is a linear regulator, not a switching regulator, so you should not see pulsations. Other than that, your understanding is fairly accurate. The TL431 will draw more and more current through the …
Spehro 'speff' Pefhany's user avatar
7 votes

FET electrostatic damage

The voltage is one thing, but remember that the human body has a certain amount of capacitance to earth, and a relatively small series resistance. That means that there is energy stored (\$C \cdot V^2 …
Spehro 'speff' Pefhany's user avatar
7 votes
Accepted

Insulated gate SCR, does it exist?

Apparently MOS-controlled thyristors were commercially available briefly, but were withdrawn due to performance issues. The structure looked like this:
Spehro 'speff' Pefhany's user avatar
2 votes
Accepted

How to measure / determine a FET's Vto (Vgs_off)?

You could just check it functionally- eg. below. simulate this circuit – Schematic created using CircuitLab If the LED lights visibly (maybe tens of uA for an efficient LED) the transistor is …
Spehro 'speff' Pefhany's user avatar
1 vote

Output characteristics of power transistors

Power MOSFETs are similar to smaller MOSFETs, just lower Rds(on), much higher capacitances and gate charge. Usually they need 10V Vgs to drive them to datasheet specifications if they are really high …
Spehro 'speff' Pefhany's user avatar
2 votes

Is there a standard way to implement desat protection on high-current FETs?

I think desaturation protection is mostly for short-circuit protection, in conjunction with short-circuit rated IGBTs and MOSFETs. The idea is to very quickly detect a severe overcurrent situation and …
Spehro 'speff' Pefhany's user avatar
5 votes

High voltage FET or other transistor

For higher voltages series combinations of individual semiconductor devices (IGBTs and thyristors, usually) are used to handle things like a 275kV DC input that must be converted to 3-phase AC. Indivi …
Spehro 'speff' Pefhany's user avatar
3 votes

MOSFET with 5 V logic, 24 V VDS / VGSS

Vgss is the maximum voltage you are allowed to put on the MOSFET gate (to source). You can put any lower voltage you like on it and the MOSFET should not fail due to excessive Vgs (it might fail for s …
Spehro 'speff' Pefhany's user avatar
2 votes
Accepted

Diodes in input protection circuits

D2 is a bipolar TVS. It's to protect against large positive or negative transients by shunting them out. There is no series impedance so it won't necessarily do well against high current or high energ …
Spehro 'speff' Pefhany's user avatar
3 votes

How to choose a "good" 3.3 V LDO and FET for low power applications?

The LDO will have to dissipate almost 0.45W nominal with a 260mA load (not including the dissipation due to Iq). It will be more if the 5V supply happens to be at the higher end of the tolerance range …
Spehro 'speff' Pefhany's user avatar
1 vote
Accepted

Depletion P-channel JFET that's saturated at \$V_{GS}=0V\$

For much lower currents than Idss, the FET is in the ohmic region with Vgs=0V so it behaves like a resistor. …
Spehro 'speff' Pefhany's user avatar
2 votes

Can I use the mosfet for 5 volt to 3.3 volt logic converter

Google MOSFET level shifter. You need to pullup to +5 to get 5V at the output. edit: Here is the first hit: It should be obvious that the way you have the MOSFET won't work (just look at the sub …
Spehro 'speff' Pefhany's user avatar

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