What is MOSFET?

[kjrocks]

Can someone give me an idea about what mosfet od sounds like? I havent played any mosfet pedals or amps so I'm just looking for a general idea. Is there a general genre or stereotypical sound that would describe it ,like 70's or 80's metal or what ever?
After reading about the upcoming Lavabox , I realized I didnt know what the heck I was reading about

 

[Pierre]

Re: What is MOSFET?

It's a type of electronics device.
FET = Field Effect Transistor. They have a Base, Drain and collector. To keep it simple it works a little like a valve. Cathode, input and output. Bring the signal in, bias it and presto it comes out bigger.
A transistor is an amplification device with a built in diode.
There are also JFETs and MOSFETS. Not sure exactly what they mean but they roughly do the same things. MOSFETS tend to be more powerful and have different circuits requirements if I remember well.

Basically it means it's solid state. SS amps use FET instead of valves.

 

[Reload in 5]

Re: What is MOSFET?

metal-oxide-semiconductor field-effect transistor

 

[Ken]

Re: What is MOSFET?

Basically it means it's solid state. SS amps use FET instead of valves.

That's pretty much all you need to know. The majority of devices I've seen for guitar applications have always been MOSFET rather than JFET.

 

[DankStar]

Re: What is MOSFET?

I'd like one of those old Mosfet Marshall heads. I realize they probably don't have the cajones of their tube brethren, but there's something about those old ones that seem cool.

 

[kjrocks]

Re: What is MOSFET?

Is there a paticular artist or song that would give me a good idea of it sound or do all manufacturers have vastly different tones?

 

[Pierre]

Re: What is MOSFET?

It's like asking how a capacitor or a valve or a resistor sounds man... It's a small part in a BIG electronics board.

 

[Scott_F]

Re: What is MOSFET?

You see them in distortion pedals quite often. two come to mind that I own or have owned recently. Full Drive 2 Mosfet annivesary edition and the new Lava Boost.

 

[kjrocks]

Re: What is MOSFET?

Apparently I have misunderstood this and thought it was more of specific type of tone you get when using mosfet equipment. I believe now its a little broader than that.

 

[Gearjoneser]

Re: What is MOSFET?

Metal Oxide Semiconductor Field Effect Transistor. From what I understand, it's a component that closely resembles the way a tube works.

The sound is generally a nice gainy tone that was one of the first SS designs to be pleasing to the ear. I remember the Marshall MOSFET's which came out during the JCM800 tube series. They weren't bad, but not great. SS didn't get good, in my opinion, till Line 6 came along.

MOSFET pedals on the other hand sound good, but I'm only basing that on hearing the Fulltone 10th Ann. Fulldrive II MOSFET.

 

[jeremy]

Re: What is MOSFET?

the blackstone mosfet overdrive sounds nice aswell

 

[Artie]

Re: What is MOSFET?

From the dept. of useless info:

An FET differs from a transistor in that you apply voltage to a transistor to turn it on. You apply voltage to a FET to turn it off. Also, due to the construction of an FET, it has a very high input impedance. That's partly what gives it its "tube-ish" characteristic. A MOSFET differs from a JFET in that the MOSFET has an additional insulating layer on the gate, (input), that gives it an even higher input impedance. 2 to 4 megohms isn't unusual.

So . . . a pedal or circuit that uses a FET on the input, won't load down the guitar signal. Assuming the engineers knew what they were doing.

 

[Pierre]

Re: What is MOSFET?

So would an OPamp be a FET with an infinite input impedance then? FET being SOME impedance but very little?

 

[Marinblues]

Re: What is MOSFET?

If I remember well a MOSFET is much more powerfull than a normal transistor. Its like a "Power" transistor. It is good for final gain stages, also because a single MOSFET can replace mutliple cascaded transistors. I think that their is some benefit in the linearity of the response.


M.

 

[Vasshu the humanoid typhoon]

Re: What is MOSFET?

OP-Amps are full of JFET's.

 

[brisk]

Re: What is MOSFET?

MOSFET is one kind of transistor.

FET means field effect transistor, which means the transitor is turned on and off using the filed effect.

MOS means metal oxide semicondutor, which means oxide is sandwitched between metal gate and semiconductor.

MOSFET is the most popular transistor now. More than 90% of transistors in chips (microprocessor, memory, etc) are MOSFET.

 

[Danglin' Fury]

Re: What is MOSFET?

In amps class I built a pretty decent distortion pedal and I used JFET's. Sounded pretty darn tube-y to me. I think somewhere on one of those stompbox websites, they claim JFET's sound closer to tubes.

OH yeah! I saw some guy on the Bay that had a MOSFET power amp and he said, and I quote:"it's not tube, it's not solid state, it's MOSFET which is better than solid state!" I asked if he stumbled on an amp that was powered by Voodoo and witch magic.:smokin:

 

[Pierre]

Re: What is MOSFET?

What's believed is that FETs of whatever kind can kinda model a preamp valve sound. But the way the whole amp REACTS is more than just valves basically.

Using SS to boost valve is perfectly good. But the opposite won't make an SS amp sound any more valvey.

 

[kobus]

Re: What is MOSFET?

For the most part transistors are primarily low voltage, 5-25 there abouts. They can process your weak pickup voltage output with more fidelity. The general difference between a TTL transistor (1st generation) and a mosfet is; How much voltage it takes to turn each of them on. The TTL is somewhere between .5 -.7 volts in general. The mosfet is approximately .2-.4 volts to turn it on. This is faster response for signal level modulation. Power transisters are another design. The electromagnetic field in the mosfet crosses the junction of the collector and the emitter allowing the electrons to rock and roll to the next whats going on eventually modulating the power transistors to bend the drivers. Comparing the transistor to a tube could be--- collector=cathode, base=grid, emitter=anode. Don't forget they come in different polarities-- NPN, PNP. This other one JFET-----Junction.