The Horizontal Cathode Follower
    The same splitting of the power supply and shifting of voltage relationships is now going to be applied to the cathode follower. But first let us look at a generic and modified cathode follower circuits to help loosen our prejudices.   

    One key to understanding this circuit is recall the cathode follower's other name, the grounded plate amplifier. It is obvious that the plate in this circuit is grounded by the second power supply. (Remember that grounded refers to AC voltages and currents.) But the cathode is free to follow the grid's voltage movement.
    If this transformation of one circuit into one radically different by simply moving the ground point troubles you, consider this: the cathode follower is effectively a grounded cathode amplifier whose output is returned to its cathode, which results in degenerating its gain (hence the name "degenerative feedback"), while lowering it distortion and output impedance. Moving the ground to the what had been the output, achieves the same degenerating task.
   Here is another mind stretcher. We start a cathode follower, i.e. grounded plate amplifier, and literally shift the ground point to the plate and move the cathode resistor to the plate.

    Nothing too startling here. In the first circuit the only deviation is the presence of two power supplies rather than just one. In the second circuit, the ground (the circuit's voltage reference point) has been moved to between the two power supplies. Both circuits function identically in terms of gain, phase, and output impedance. Now lets go horizontal.
    If we take the horizontal grounded cathode amplifier and move the ground to what was the output, we will have converted the circuit into a horizontal cathode follower.
    The voltage relationships have certainly changed. The input is now at ground level as is the output. But the circuit functions identically with the more conventional cathode follower in terms of gain, phase, and output impedance.