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Dragging this old thread back to life. Post #7 shows the plate voltage along the bottom of the graph. In the past I have been told several different things. One person tells be to plot the B+ right from the rectfier and that is the B+ that I use in the graph and yet another person tells me to use the B+ just before the plate resistor which can be somewhat lower. Which is it?
The graph in post 7 is a set of plate curves , typical of what is in most tube datasheets. They are manufacturers' data intended for use by those interested in the tube itself and don't include assumptions about the configurations of infinite possible circuits the tube might be used in.
"Plate Voltage" is voltage measured at the plate and "Plate Current" is is current measured at the plate.
The material linked in post#75 is written by a fine engineer with us mere solder slingers in mind and is worth taking the time to download and read.
Not unless I'm constrained by an existing power supply or or PS parts I've already decided to use no matter what. Otherwise, start with the most suitable operating point for the applied use of the chosen tube and then come up with the power supply to provide what is required.
Important also to note that requirements for resistive and inductive loads can and do differ.
To Burnedfingers question,
remember that B+ refers to the tube's plate supply (originally B for battery) , the output of which will vary across the supply in accordance with Ohm's law. In the case of a resistively loaded triode, at quiescent operating point the B+ supply output voltage appears at the PS connection to the plate resistor. If the tube goes into cut-off, it appears at the plate side (as there is no drop across the resistor). So, in this way, B+ output voltage varies with series resistances of the supply and the current draw through them. When working out the design and parts values don't look at the supply as separate from the signal circuit. The whole thing is calculated together for its values at the desired steady state operation. I hope I said that right. When I first started doing my own circuits it was something I needed to be reminded of again and again until it became a natural way to think. For me it was the idea of an overall state of the whole circuit that was the thing I needed to grasp. I hope this is useful.
Important also to note that requirements for resistive and inductive loads can and do differ.
To Burnedfingers question,
remember that B+ refers to the tube's plate supply (originally B for battery) , the output of which will vary across the supply in accordance with Ohm's law. In the case of a resistively loaded triode, at quiescent operating point the B+ supply output voltage appears at the PS connection to the plate resistor. If the tube goes into cut-off, it appears at the plate side (as there is no drop across the resistor). So, in this way, B+ output voltage varies with series resistances of the supply and the current draw through them. When working out the design and parts values don't look at the supply as separate from the signal circuit. The whole thing is calculated together for its values at the desired steady state operation. I hope I said that right. When I first started doing my own circuits it was something I needed to be reminded of again and again until it became a natural way to think. For me it was the idea of an overall state of the whole circuit that was the thing I needed to grasp. I hope this is useful.
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