On Wed, 26 Sep 2007 16:10:23 -0700, Telstar Electronics
wrote:

|On Sep 26, 3:51 pm, james wrote:
| For either circuits, bad A and B, to work properly, the D1 diode
| current should be ten times the peak instantaineous base current of
| the RF power transistor. This type of biasing is good for low power RF
| devices. When dealing with large power devices, ie in the 100W and
| more class, this is not a good bias as the wasted heat in VR1 and D1
| is very inefficient and prone to failure. Also there is no protection
| should a voltage spike on the DC supply propogate through. Most
| bipolar RF device do not like more than about 4 VDC base/emmiter
| voltage. Both circuits have no provisions for limiting the bias
| voltage in such a manner to cause permanent damage to the base/emitter
| junction.
|
|
|OK... I don't agree with most of what you've said here... but thanks
|for your explanation.
|-------------

Brian

Believe what you want, but there are basic principles of electronics
that you can not deny. Also try and read spec sheets. They don't put
maximum base emmitter voltage in them for the pure heck of it.

james