A TRIODE is basically a diode with a control grid mounted between the plate and the cathode. The
control grid gives the triode the ability to amplify signals.
The OPERATION OF A TRIODE depends on the ability of the control grid to either increase or
decrease conduction through the tube in response to an ac input signal. The output voltage is developed
across the tube between the cathode and plate because of the voltage drop across the plate-load resistor
changing as the plate current responds to the input signal.
TUBE BIASING is the process of placing a dc voltage, usually negative, on the grid. Bias has
several functions in circuit design. Biasing may be divided into two types: fixed and self. Tubes using
fixed bias have a dc voltage applied to their control grids from an external source such as a battery. Self-