Fixed/cathode bias and AC [message #9083] |
Tue, 19 July 2005 09:44 ![Go to next message Go to previous message](/forum/theme/AudioRoundTable/images/down.png) |
Manualblock
Messages: 4973 Registered: May 2009
|
Illuminati (13th Degree) |
|
|
Thanks all for doing a great job in explaining this. So fixed bias is derived from a voltage divider and a cap on the input AC signal. It has the advantage of allowing the tube to be operated at a fixed Vg. Self-bias uses a resistor to react to changes in the signal by following Ohm's law and causing a plate voltage drop to change with the Vg. The self-bias is self regulating and must operate in class A. It is easier to design due to the self-regulating properties of the circuit. AC component on the plate voltage is removed by the by-pass cap. Now why would anyone go to the trouble of using grid leak bias when they could just use the cathode bias? It seems so simple.
|
|
|