second breakdown in class D power amplifiers

[ifrah jaffri]

what is meant by second breakdown in switching power amplifiers? i read that since their is potential cause of damage due to second breakdown in class D voltage switching amplifiers, Class E power amplifiers were introduced.. can anyone kindly explain me what does it mean?

 

[godfreyl]

There's a short explanation here. Datasheets for power transistors give more detail about their SOA.

 

[ifrah jaffri]

if second breakdown is due to current concentration in base emitter junction then how can we justify this concept in mosfets ? moreover, why we are calling it second breakdown ? any reason of using the term second here?

 

[schmitt trigger]

For Class E, there is a good technical and mathematical explanation in the link, with emphasis on "technical and mathematical"

**broken link removed**

 

[godfreyl]

...how can we justify this concept in mosfets ?

MOSFETs don't suffer secondary breakdown. You would know that already if you had bothered to follow the link I gave earier.

 

[ftsolutions]

MOSFETs don't have secondary breakdown like BJTs, but they can suffer failures from developing localized "hot spots" that is exacerbated by their technology. Older style, power MOSFETs of the lateral type were most resistant to this, but as technology has moved toward vertical architectures and smaller, denser gate structures, the possibility of this happening is significantly increased, especially when operating the device as a linear amplifier and not as a switch.