SCRs and Mosfets?

[thecritic]

As far as I have known, SCRs (type of a Thyristor), like a Mosfet, have a gate terminal, which when provided with sufficient Voltage will switch on the device for conduction in the forward Region. But unlike Mosfets, they latch.

I simply wanted to ask, is there some situations when only SCRs OR Mosfet will do the work but not the other? I mean, when latching is required, some secondary circuitry could be added to bring about the latching.

Also, In general practice, where is SCR preferred and Where is Mosfet preferred?

Also, IGBTs are some sort of improved Mosfets, am i right?

 

[Jaguarjoe]

MOSFETs are not desireable at high voltages because their on resistance increases with its voltage rating. This causes higher power dissipation. IGBT's have a gate like a MOSFET but are BJT's. Their Vces is not very high making them more efficient at higher voltages. SCR's are also good at higher voltages.

 

[crutschow]

SCRs are simple to use when you are switching AC, such as in phase-control dimmers, since they automatically shut off at every cycle when the current goes through zero. Using a transistor for the same purpose would require significantly more circuitry.

 

[thecritic]

And what about Pricing?

 

[Jaguarjoe]

A 1 amp 200 volt MOSFET is 0.62 USD
A 1 amp 200 volt SCR is 0.37 USD
A 2000 amp 2000 volt hockey puck SCR is $1000.00 USD There are no MOSFETs that compare