| 摘要 |
PURPOSE:To prevent latchup by forming a drive MOS transistor directly on a semiconductor substrate to eliminate the variation in the potential of a junction at the periphery of a drain due to a trigger current. CONSTITUTION:When a resistor 11 (a thermal head) is driven by an N-channel MOS transistor 3 of a drive element, a gate is varied by the output 7 of a level shift 10 to switch the transistor 3, thereby controlling the resistor 11. The substrate is altered to P type substrate so that an N-P-N type transistor is eliminated at the periphery of the element 3, thereby eliminating a 4-layer structure of P-N-P-N causing a latchup at the periphery of the drain of the element for switching a large current by the high voltage so that the trigger current from the drain 4 is absorbed to the substrate 20. Since the P-channel MOS transistor is used as the drive element, similar operation can be provided even if the N type substrate is employed. |
