[dgardner]

I just got my long-awaited-for engineering samples of some new high performance BJT's designed for high-end output stages. These were possible candidates for the Gilmore Uberamp. Anyone else out there considering moving into higher wattage Class-A designs beyond the dynalo and dynahi?

http://www.onsemi.com/pub/Collateral/AND8196-D.PDF

 

[amb]

I am toying with the idea of a fully discrete amp with MOSFET output, where thermal runaway isn't an issue.

At any rate, it's about time for a device such as the On Semi thermaltrak BJTs. I had always considered the need to put a biasing transistor or diode(s) on the heat sink along with the output devices (to manage BJT thermal runaway) a bit of a kludge. Having them built into the output transistors themselves is definitely going in the right direction.

As for an application of these in class A designs, though, I think it's less necessary than it is in class AB designs. Class AB amps are subjected to a far greater temperature variability that's dependent on output and load, whereas class A is just hot all the time. It's actually a lot easier to deal with the latter.