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Understanding Class A triode operation...and PSU requirements

Posted by Jayme (A) on February 1, 2007 at 13:50:39

So...I am trying to get a mental handle on what is happening from a Power Supply perspective during normal operation of a driver stage.

Given a triode operating in Class A, with the B+ attached to the anode, the input signal attached to the grid, and a biasing resistor attached to the cathode and grounded. The output is also attached to the anode, with a DC blocking cap to prevent B+ voltage.

1) Is the voltage and current drawn from the B+ (under class A operation) always a fixed amount? Or does it vary, even slightly?

2) Can operation of the triode be thought of as a Voltage Shunt...so that a given amount of voltage is shunted through the tube, and modulated by the grid in response to the input voltage, with the remaining voltage component serving as the "amplified input signal" and traveling through the output cap?

What I am trying to understand in terms of the PSU in a Class A preamp is...does the PSU have to be critically damped to prevent ringing if voltage/current changes? Or, does this not matter, as intrinsically, the voltage/current drawn from the PSU never changes, and thus makes this point moot?

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