Undecided power amlifiers

[crisrole]

Hello everyone

Many power amp.circuit diargrams use transistors on outputs,, and others are mosfets.. i am thinking of these two device which is better,, some help please..thanks

 

[Nigel Goodwin]

Hello everyone

Many power amp.circuit diargrams use transistors on outputs,, and others are mosfets.. i am thinking of these two device which is better,, some help please..thanks

Neither really - both have advantages, and both have disadvantages - but there's FAR more amplifiers out there using transistors than using MOSFET's.

 

[KeepItSimpleStupid]

MOSFETS are more expensive to control because of the need of extra power sources.

MOSFETS in switching supplies is a natural.

With a MOSFET the voltage is the controlled variable and with BiPolar transistors, the current is the controlled variable. Whether that makes a difference is unknown, but I suspect the reason MOSFETS aren't used in outputs is cost.

 

[crisrole]

thanks for your replies;;I ask this because as for now,I encounter mostly transistors on output of an amp. One engineer told me before that mosfets are far better than transistors when talking about amplifiers..

 

[KeepItSimpleStupid]

Take a look at this search: https://search.yahoo.com/search?ei=UTF-8&fr=ytff-tyc&p=mosfets+vs+tubes

 

[Nigel Goodwin]

thanks for your replies;;I ask this because as for now,I encounter mostly transistors on output of an amp. One engineer told me before that mosfets are far better than transistors when talking about amplifiers..

A tiny number of people think that, and it's not really true at all.

Most designs use bipolar because they are cheaper, and more reliable generally - certainly devices that use MOSFET's seem to die at least as much as bipolar's, and probably slightly more (and repair costs are considerably higher).

 

[Tann-44]

It would depend on what type of circuit your aiming for...or buy a amplifier kit from velleman'

 

[Tann-44]

I've worked on countless high end amplifiers over the years...yes mosfets are a little more forgiving if you short them.. transistors will die fast...

 

[unclejed613]

mosfet amps CAN be less expensive to build, because the output devices can be driven from the voltage amplifier stage, and not needing driver transistors to boost the current. however, they often require several volts of gate bias, so the output doesn't swing rail to rail. bipolar transistor amps swing to within a few tenths of a volt of the rails. the crossover region is not as smooth a transition with mosfets as it is with bipolars, adding a small amount of distortion at low signal levels, those are the most commonly considered tradeoffs. there are two types of mosfets used in amplifiers, Vfets and lateral fets. the lateral ones require little or no thermal compensation, the Vfets do require a thermally coupled bias circuit the same way bipolar transistors do. laterals are much more expensive than Vfets (Vertical fets)

mosfets are more forgiving of difficult loads because they don't have a second breakdown region limiting their safe operating area. going into the second breakdown region with a bipolar is "instant death".