On Tue, 25 Sep 2007 05:43:22 -0700, Telstar Electronics
wrote:

|On Sep 24, 2:42 pm, Frank Gilliland
|wrote:
| So you claim it doesn't work because one diode will "hog" the current?
| Well, that's the point! D1 "hogs" the current and establishes a fixed
| voltage for the base of TR1!!!
|
|As usual Frank you are missing the important point here. That point
|being that you can't simply parallel two diodes... and have them share
|currents. This would have to be done in order for any tracking between
|the two. The problem is that one diode will always turn on before the
|other... and take all current. Now I ask you... where is the sharing/
|tracking in that scenario? The answer is: there is no sharing/
|tracking... because one diode with the lowest drop will hog the entire
|current... and the other diode will be off. this is why the gentleman
|on the web page link that YOU provided says it that scheme works like
|crap. He's absolutely right!
|www.telstar-electronics.com
|
|-------------


Bovine excrement. Ever heard of equalizing of current through a series
resistance? Often called a ballast resistor. Used quite often in power
transistors where there are several base/emiter pn jumctions.

james

On Tue, 25 Sep 2007 07:08:51 -0700, Telstar Electronics
wrote:

|On Sep 25, 8:42 am, Frank Gilliland
|wrote:
| Amazing. Two major bungles within one month. First you couldn't
| recognize a simple voltage multiplier, and now you show that you can't
| even understand the basic principle of diode biasing of a transistor.
|
|Frank, again you resort to degrading statements in an attempt to shift
|the focus and avoid the topic.
|You have suceeded... end of conversation with you.
|www.telstar-electronics.com
|-------------

No Brian

He is quite on topic. You are failing to comprehend a very simple
basic understanding of the biasing of a transistor.

james

On Tue, 25 Sep 2007 07:08:51 -0700, Telspam Electronics
wrote in
om:

On Sep 25, 8:42 am, Frank Gilliland
wrote:
Amazing. Two major bungles within one month. First you couldn't
recognize a simple voltage multiplier, and now you show that you can't
even understand the basic principle of diode biasing of a transistor.

Frank, again you resort to degrading statements in an attempt to shift
the focus and avoid the topic.


The topic is the concept of using a diode to bias a transistor, a
concept understood by any first-year electronics student.

But not you.

The BE junction stays at or above quiescient current BECAUSE the diode
is hogging the current. It even says that in the article (that you
obviously didn't understand).

Two diodes..... sheesh..... I'll bet you've never seen a Vbe curve,
either.


You have suceeded... end of conversation with you.


Well, since that's the closest thing to an admission of ignorance that
you are capable of, I'll take all nine square feet...... ROTFLMMFAO!!!

On Sep 25, 9:37 am, james wrote:
Bovine excrement. Ever heard of equalizing of current through a series
resistance? Often called a ballast resistor. Used quite often in power
transistors where there are several base/emiter pn jumctions.

OK James... less not discuss ballasting... because that has no bearing
in this particular discussion. Maybe you can tell us how the diode
method of biasing shown at http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm
(bad circuits section) works. And since you think that circuit works
well. Please tell us why.
www.telstar-electronics.com

On Tue, 25 Sep 2007 08:09:50 -0700, Telspam Electronics
wrote in
. com:

On Sep 25, 9:37 am, james wrote:
Bovine excrement. Ever heard of equalizing of current through a series
resistance? Often called a ballast resistor. Used quite often in power
transistors where there are several base/emiter pn jumctions.

OK James... less not discuss ballasting... because that has no bearing
in this particular discussion. Maybe you can tell us how the diode
method of biasing shown at http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm
(bad circuits section) works.


Holy ****..... Brian flunked first-year techie school!!!!

On Tue, 25 Sep 2007 08:09:50 -0700, Telstar Electronics
wrote:

|On Sep 25, 9:37 am, james wrote:
| Bovine excrement. Ever heard of equalizing of current through a series
| resistance? Often called a ballast resistor. Used quite often in power
| transistors where there are several base/emiter pn jumctions.
|
|OK James... less not discuss ballasting... because that has no bearing
|in this particular discussion. Maybe you can tell us how the diode
|method of biasing shown at http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm
|(bad circuits section) works. And since you think that circuit works
|well. Please tell us why.
|www.telstar-electronics.com
|------------

Actually quite simple if you understand nodal analysis. Per Kirchoff's
Laws the total current leaving a node must equal the current entering
a node. The particular node that is of interest is in bad circuit A,
is the junction of VRI, D1 and the base of the transisitor. For DC
analysis the cap is an open circuit and the RFC is essentially a
short. The current through D1 is set by the value of VR1, the supply
voltage and the internal pn junction of the diode. The voltage drop
across D1 is determined by the current flowing through the diode. In
turn this sets the Vbe voltage of the base/emmitter PN junction. The
instantaineous base/emmiter current varies with RF drive level. Should
this current exceed 1/10th the current through D1, then D1 starts to
loose regulation. This is the basic workings of a shunt regulator. Any
good first year tech should know this.

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.

james

On Tue, 25 Sep 2007 08:20:48 -0700, Frank Gilliland
wrote:

|On Tue, 25 Sep 2007 08:09:50 -0700, Telspam Electronics
wrote in
.com:
|
|On Sep 25, 9:37 am, james wrote:
| Bovine excrement. Ever heard of equalizing of current through a series
| resistance? Often called a ballast resistor. Used quite often in power
| transistors where there are several base/emiter pn jumctions.
|
|OK James... less not discuss ballasting... because that has no bearing
|in this particular discussion. Maybe you can tell us how the diode
|method of biasing shown at http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm
|(bad circuits section) works.
|
|
|Holy ****..... Brian flunked first-year techie school!!!!
|
|-------------

I am not sure he got far enough to flunk first year. Maybe after teh
first half of the first year. Yes he seems to not understand a basic
shunt regulator circuit or Kirchoff's laws.


james