TEMPERATURE CONTROL CIRCUIT FOR CRYSTAL OSCILLATOR WITH THERMOSTATIC TANK

To provide a temperature control circuit for a crystal oscillator with a thermostatic tank capable of improving temperature adjustment resolution in the vicinity of a minimum point temperature of a frequency-temperature characteristic of a crystal vibrator, and thereby outputting a stable frequency signal.SOLUTION: A temperature control circuit comprises: a first resistor R1 whose one end is supplied with a power supply voltage; a thermistor TH whose one end is connected with the other end of the first resistor R1 and whose the other end is grounded; a digital potentiometer Rpo connected in parallel with the first resistor R1; a second resistor R2 whose one end is supplied with the power supply voltage; and a third resistor R3 whose one end is connected with the other end of the second resistor R2 and whose the other end is grounded. One input terminal of a differential amplifier IC receives input of a voltage between the other end of the first resistor R1 and the one end of the thermistor TH, and the other input terminal receives input of a voltage between the other end of the second resistor R2 and the one end of the third resistor R3. A base of a power transistor receives input of an output of the differential amplifier, and a collector is connected with a heater resistor.SELECTED DRAWING: Figure 1 【課題】 水晶振動子の周波数温度特性の極小点温度付近における温度調整の分解能を向上させ、安定した周波数信号を出力させることができる恒温槽付水晶発振器の温度制御回路を提供する。【解決手段】 電源電圧が一端に供給される第１の抵抗Ｒ１と、第１の抵抗Ｒ１の他端に一端が接続し、他端が接地するサーミスタＴＨと、第１の抵抗Ｒ１に並列に接続されたデジタルポテンショメーターＲpo と、電源電圧が一端に供給される第２の抵抗Ｒ２と、第２の抵抗Ｒ２の他端に一端が接続し、他端が接地する第３の抵抗Ｒ３とを備え、差動増幅器ＩＣの一方の入力端子に、第１の抵抗Ｒ１の他端と前記サーミスタＴＨの一端との間の電圧が入力され、他方の入力端子に、第２の抵抗Ｒ２の他端と第３の抵抗Ｒ３の一端との間の電圧が入力されて、パワートランジスタのベースに差動増幅器の出力が入力され、コレクタにヒーター抵抗が接続された温度制御回路としている。【選択図】 図１