| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a heater drive circuit by which the temperature difference between a heater temperature and an outside temperature can be made constant. SOLUTION: A fixed resistor RR and a temperature measuring resistor RR are connected across the - terminal of an operational amplifier OP2 and a ground. A heater resistor RH is connected across the + terminal of the operational amplifier OP2 and the ground. A fixed resistor Ra is connected across the + terminal of the operational amplifier OP2 and a transistor Q2. A variable resistor Rb is connected across the - terminal of the operational amplifier OP2 and the transistor Q2. When the fixed resistor RU does not exist, the potential difference between a point A and a point B becomes zero, a prescribed current flows to the heater resistor RH, and a heater is heated. In addition, when the fixed resistor RU is connected in series with the temperature measuring resistor RR, the potential difference becomes large by a portion of the inserted fixed resistance RU. As a result, the transistor Q2 increases a current to the heater resistor RH more than the prescribed current in such a way that the potential difference becomes zero, and a heater temperature rises with reference to an external temperature by a portion of the inserted fixed resistor RH.</p> |
