| 摘要 |
Provided is a thermal head driving IC for supplying voltage to a plurality of heating resistors each controlled by a driving MOS transistor, including a switch for making and breaking between a substrate and a source of the plurality of driving MOS transistors. In a case where the plurality of heating resistors are activated, the plurality of driving MOS transistors are turned on and the switch is turned off, a substrate is floated. As a result, a substrate potential is forward-biased against the source by a substrate current generated in a high-electric-field depletion region near the drain, and a parasitic bipolar transistor turns on, whereby both the plurality of driving MOS transistors and the parasitic bipolar transistor turn on. In a case where the plurality of heating resistors are not activated, a signal for turning off the plurality of driving NMOS transistors is given, and the switch is turned on.
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