bi polar transistors vs mosfet

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Multi choice :D

You could argue both are correct or equally neither are correct. Not enough parameters are given to say either statement is true or false.

What I was trying to get across to the op was the basics in a simple to understand form.
 
Ive heard that mosfets produce a better sound in amps is this true? do they work on the same principle?

The "sound" of a BJT or mosfet will be completely swamped by the local and global feedback used in any decent amplifier design. BJTs and mosfets both have other characteristics that would lead the designer to choose one over the other. Without feedback both device types would sound terrible on account of their poor linearity.

I personally like lateral mosfets for their speed, ruggedness and easy drive requirements. Others may prefer BJTs for their cost, availability and stability.
 
It is depend on implementation.

If you use it for buffer without global negative feedback and error correction, you should easily find the sound different.

If you use huge loop gain in global negative feedback with or without error correction, if slew rate and signal to noise ratio almost same, you will very difficult to find sound different.

Event if you use BJT only, you can find the sound different if the implementation is different.

Ordinary person usually make conclusion using statistic only, because they do not understand about engineering. If you use statistic ONLY in engineering, it will lead you to WRONG conclusion. Engineering is different from social or economic.
 
The task of the designer is to develop an amplifier with the given characteristics using the available parts.
It is up to the engineer to implement what he has planned in practice.
The marketer comes up with a hook to catch customers.
The user chooses from the offers on the market (or thinks he chooses himself))).
DIYer does for his own pleasure (and recognition of his own kind))).
 
Why bother with which is best?
As DIYers, we should be happy while we still have the choice to experiment with.
It might not last.

This is true, high voltage BJT transistors are on the endangered species list, there's one manufacturer of lateral mosfets and that leaves a multitude of vertical mosfets mostly used for high speed switching applications.
 
Ive heard that mosfets produce a better sound in amps is this true? do they work on the same principle?
This question arose after the well-known Hitachi MOSFETs appeared in late 1970s - go to
Hafler (HITACHI) 2SJ49 and 2SK134 NOS Power MOSFET pair | #68189805

Today the question must be asked again in order of many obsolete ones, assumed that new amplifier developments and new diy projects are started, if desired, no expensive NOS parts, but those from ongoing production to use.

In this case I want to know good delivery sources for MOSFET's of currently manufacturing (BjT power transistors I order at Profusion).
BUZ900 and BUZ901 and the successors from Exicon/Magnatec/semelab (AlFET) all obsolete in the meantime - go to
NOS ALFET ALF08P16V and ALF08N16V
Which currently manufactured MOSFET's are good available for new projects and replacements ?
 
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what would be the reason why they used FET'S here instead of BJT'S do you think? its a NAD 3240PE
 

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Those are used as muting devices and operate a bit like a switch. When on it has quite a low resistance and when off it has almost infinite resistance. That kind of (small signal) JFET is symmetrical and the Drain and Source are only notional markings. You can not tell D from S by testing (there is no difference anyway) and the device works the same in both directions which is perfect for a series switch.

The JFET is the ideal device for that application. Using ordinary transistors would be very non linear and you would have issues with voltage offset at the output caused by having to inject base current. It would also need low impedances around it to work in any way at all.

So the FET wins here ;)
 
FETs are linear when used as switches in series mode. A constant ON resistance, and just a small capacitor when OFF. When used as shunt switches, however, bipolars are better because you want a VERY low ON resistance which doesn’t have to be remarkably linear. And there are small signal low capacitance types (a pf or two Cob) that can get down to single digit ohms to get signal leakage into the noise floor. That can often times be better than the leakage thru OFF state FET capacitance, depending on source and load impedances. You will often see both types used in muting circuits, maybe even both together where leakage and isolation requirements are strict and difficult. I tend to use bipolars myself. Shunt mode with two stages has really excellent isolation.