| 摘要 |
PURPOSE:To dispense with a constant voltage generating circuit and to realize a temperature sensing circuit of high precision with only the dimensional ratio of transistors by a method wherein a current output type D/A converter is provided and a current which is made to flow through a resistor is optimized. CONSTITUTION:A P-type MOS field effect transistor 11 of a temperature sensing means 1 is so designed in size as to enable a micro current of 1muA or so to flow, and the voltage of a terminal 13 varies ranging from 2.3 to 3.5V when the ambient temperature is made to change from -40 to 85 deg.C. On the other hand, when the analog input voltage range of an A/D converter 4 is identical to the output voltage range of the terminal 13, the resolving power of the temperature sensing means 1 can be most effectively set. The setting concerned can be realized as follows: a P-type MOS field effect transistor 45 is properly designed in size so as to feed a current that makes the output voltage of a resistor 44 equal to 2.3V to the resistor 44, where the resistor 44 generates one of the input voltages of a comparator 43: and the output current range of a current output type A/D converter 42 is so set as to enable a voltage drop of 1V or so to occur in the resistor 44. |
