Does biasing at max dissipation guarantee class A operation?
Just because you are biased at max dissipation does not mean you are class A! You must be in the region where the voltage swing is symmetrical and biased in the center of the range, where plate current flows for all unclipped output. Biasing to a high voltage and low plate current whose product equals the maximum plate dissipation might not allow this, because, although you are at max plate dissipation, the bias point is such that plate current will flow for an appreciably less time on the negative signal swing (cutoff) than it will on the positive signal swing (saturation), and *no* load line can be found that will allow symmetrical swing, or it will be in such a non-linear portion of the curves as to be unusable. This is because the plate voltage is too high, and the max allowable current without exceeding dissipation limits is too low. The same thing can occur on the other end of the scale, where you can reduce the plate voltage to a point that the max dissipation current will excee
