Grid bias could also be achieved by using an applied grid voltage in addition to the control voltage.
If the grid voltage is always negative with respect to the cathode the class is AB.
Changing the grid voltage will change the plate current; by suitable choice of a plate load resistor, amplification is obtained.
Temporary or long term reduction of an electrical grid voltage, a brownout (electricity)
In fact, by increasing plate and grid voltages in the amplifier, I believe that I can burn out a man's brain.
Turbines generate electricity at 12kV which travels via underground cables to the substation where it is stepped up to 132kV to match the grid voltage.
Each turbine has a transformer inside the tower which transforms the voltage to the 20 kV internal grid voltage of the wind farm.
This can swamp the grid power supply if this reverse current gets too high, changing the grid (bias) voltage and, consequently, the operating point of the tube.
The grid voltages employed are largely dependent on the path length between these substations and 200-700 kV system voltages are common.
In transmission applications, the SVC is used to regulate the grid voltage.