The intersection of the diode plate line with the resistor load line marks the idle (or quiescent) current through this circuit and sets the voltage division point between these devices.

  With the advent of computer based curve tracers, we should experiment with displaying the tube's plate curves in an more informative way the usual 5 to 10 lines. With color printing no longer being the big cost issue as we move into a paperless society, color can be used to display relative impedance of any point on a line. For example, lighter for low impedance and darker for high impedance. Hundreds of lines instead of just 10 lines would give a quick visual clue to the sweet stops on the curves by revealing the most consistent color.

Triodes
   The diode is transformed into a triode with the addition of a spiral of wire wrapped about its cathode called a "grid." It is the grid that allows us to control the flow of current through the triode and thus makes amplification possible. If the grid, however, is shorted to the cathode (or even to the plate, NOT Recommended), we are back to having just a diode. But if the voltage present on the grid can be adjusted, we have the famous triode plate curves.
   Each line represents the current flow at a given plate voltage with a given fixed grid voltage. The usual practice is to start with the grid voltage equal to 0 volts and then each successive line equal to an equally spaced decrement of grid voltage, such as -2, -4, -6, -8 volts

   Next month, we will continue with the graphing of triodes.

                              //JRB

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