What is a MOSFET amp?

[memphisman 10+ year member]

^^^ As the title states, what exactly is a mosfet amp? Is it some kind of weird package or just an advertising toy?

Click to read more...

 

[Lil Poot 5,000+ posts]

wikipedia is your friend

 

[hoxie08 5,000+ posts]

a mosfet is what is used to amplify the signal... pretty sure just about EVERY amplifier has em in it.

 

[memphisman 10+ year member]

wikipedia is your friend

Never thought of that!!! lol thaks bud!

 

[brtnboarder3241 5,000+ posts]

a mosfet is what is used to amplify the signal... pretty sure just about EVERY amplifier has em in it.

lol.. THIS CANT BE TRUE...

 

[brtnboarder3241 5,000+ posts]

http://en.wikipedia.org/wiki/Mosfet

 

[memphisman 10+ year member]

Power MOSFETs have a different structure than the one presented above.[36] As with all power devices, the structure is vertical and not planar. Using a vertical structure, it is possible for the transistor to sustain both high blocking voltage and high current. The voltage rating of the transistor is a function of the doping and thickness of the N epitaxial layer (see cross section), while the current rating is a function of the channel width (the wider the channel, the higher the current). In a planar structure, the current and breakdown voltage ratings are both a function of the channel dimensions (respectively width and length of the channel), resulting in inefficient use of the "silicon estate". With the vertical structure, the component area is roughly proportional to the current it can sustain, and the component thickness (actually the N-epitaxial layer thickness) is proportional to the breakdown voltage.

It is worth noting that power MOSFETs with lateral structure are mainly used in high-end audio amplifiers. Their advantage is a better behaviour in the saturated region (corresponding to the linear region of a bipolar transistor) than the vertical MOSFETs. Vertical MOSFETs are designed for switching applications

 

[thch 10+ year member]

well, thats one case.

FETs have become VERY popular in power supply design. because 12V isn't enough to give you 50V AC directly, all high power car amplifier will have a power supply to convert the 12V into something more like +50V and -50V.

BJTs are still very popular for the actual amplifier, and the debate to BJTs vs FETs comes up from time to time.

FETs are also used extensively in class D amps, again for the very nice switching characteristics.

you may see things like "MOSFET power supply" on some amplifiers.

-- edit. yes, it is a marketing gimmick. It sounds high-tech. nearly 100% of all aftermarket amplifiers over 20W use them, and they are both cost effective and highly suited to use in these amp's power supplies.