Universal loadline calculator for vacuum tubes

This calculator allows you to compute and tune loadline and operating point of various vacuum tubes.

It considers both reactive loads (for vacuum tubes used in output power stages) and resistive load (for the other stages).

You can:

  • choose among most common vacuum tubes,
  • set the operation modality, among ultralinear (for power tubes with reactive load), pentode, and triode mode,
  • set the B+ voltage, the screen voltage, the screen tap, the quiescent bias current.

The calculator:

  • plots the anode characteristic graph, for the chosen operation modality,
  • plots the reactive loadline for reactive load,
  • plots the DC and AC loadlines for resistive load,
  • highlights the operating point,
  • highlights the needed output headroom,
  • estimates the grid bias voltage,
  • estimates the maximum expected output power, in case of power tubes.

The underlying model and equations, for tracing anode characteristics curves, are those discussed by Norman Koren, in his web site.

Select a Tube:
Operating mode:
B+ (V): Grid Bias Voltage (V):
Operating Point: Ia:
Max Output Power (W):
Load (Ohm):
Next stage AC Impedance (Ohm):
Screen Voltage (V):
UltraLinear tap (%):
Out. headroom (+/-V):

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