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This calculator calculates some key values for operation of a valve RF amplifier with resonant load, and points on an intitial load line for further modelling with the Designing the operating point for a grounded grid Triode Class B RF amplifier.
Key assumptions of the calculator are:
Class AB RF amplifiers usually operate so close to Class B conduction angle that Class B assumptions are quite reasonable for an intitial load line estimate, in fact the greatest source of error is the device non-linearity rather than conduction angle assumptions.
The method used by this calculator is described in detail at Designing the operating point for a grounded grid Triode Class B RF amplifier.
The calculator does not do a lot of error checking, if you enter nonsense, it will produce nonsense. NaN means not a number, check the input values.
All values are peak unless annotated otherwise. RF annotation means Radio Frequency component at the fundamental frequency.
| Input field | Meaning |
| Vs | Anode DC power supply voltage (loaded) |
| Vgk | Peak grid - cathode voltage (not required for common cathode configuration) |
| Vak min | Minimum instantaneous anode - cathode voltage |
| Po | Required RF power output |
| NWeff | Output network efficiency (typically ~95%) |
| Class | Amplifier class (A, B, C) |
| Configuration | Amplifier configuration (CC, CG) |
The ARRL Handbook has a formula with a bunch of K factors for different
classes, and they explain
as K = a constant that approximates the (fundamental) RMS current to dc (sic) current ratio
appropriate for each class.
Their factor K captures more than that, even if
poorly. Their method implies that Vak min is proportional to DC supply voltage,
but it isn't. The ARRL method is not sensitive to whether a PA is common cathode
or common grid configuration. The method described in this article and used in
the calculator is a more accurate model than the ARRL formula.
Many other design tools are based on the ARRL's method and K factors, or similar.
| Version | Date | Description |
| 1.01 | 22/05/2011 | Initial. |
| 1.02 | ||
| 1.03 | ||
| 1.04 | ||
| 1.05 |
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