In this embodiment, the second transistor terminal 28A2 of the first depletion mode MOSFET 24A shares a common source terminal with the second transistor terminal 28B2 of the second depletion mode MOSFET 24B. FIG. 9B shows a front plan view of the diffusion layer diagram of FIG. 9A, including the first and second head terminals 20A and 20B, the resistor 32, and the positive voltage 34 applied to t