Temperature characteristic compensation apparatus
The invention provides a temperature characteristic compensation apparatus that correct temperature characteristics of control circuits using thermal sensors into linear or optional temperature gradients to guarantee correct and stable operations thereof. It is equipped with a temperature characteristic compensation apparatus, that can include: a constant current source in which a plurality of constant current paths that include the constant current path having a first resistance being interposed therein, which compose current mirror circuits in multiple stages, a band gap circuit formed from a pair of transistors that are connected to the constant current paths, respectively, and a voltage follower circuit, including the aforementioned constant current source and the band gap circuit that provide a reference voltage, which supplies the reference voltage at a low impedance. The ratio between the first and second resistances can be freely selected in connection with the ratio between emitter areas of the pair of transistors (the size ratio of the two transistors), such that a gradient of temperature coefficient of the output voltage can be flexibly set.
1. A temperature characteristic compensation apparatus that offsets or adjusts temperature characteristics of main parts of an electronic apparatus, the temperature characteristic compensation apparatus comprising:
a constant voltage source that outputs a reference voltage that is generated based on a constant voltage obtained by a band-gap circuit;
a voltage follower circuit that stably supplies the reference voltage output from the constant voltage source with a low impedance; and
a temperature gradient managing device that flexibly manages a temperature coefficient of the reference voltage,
the constant voltage source having:
a constant current circuit including a plurality of constant current paths that include a first current path having a first resistance being interposed therein, and the band gap circuit formed from a pair of transistors in a current mirror configuration that are interposed in the plurality of constant current paths, respectively; and
a second constant current path that is connected in cascade to the constant current circuit, formed in a multiple-current mirror configuration and has a second resistance interposed therein,
the temperature gradient managing device that flexibly selects a ratio of the second resistance with respect to the first resistance based on a predetermined formula relating to a size ratio of the pair of transistors, and
a one-shot trigger circuit that provides a shock voltage to bases of the transistors, which is required to turn ON the transistors to turn the band gap circuit from OFF to ON.
2. A temperature characteristic compensation apparatus that offsets or adjusts temperature characteristics of main parts of an electronic apparatus, the temperature characteristic compensation apparatus comprising:
a constant voltage source that outputs a reference voltage that is generated based on a constant voltage obtained by a band-gap circuit;
a voltage follower circuit that stably supplies the reference voltage output from the constant voltage source with a low impedance; and
a temperature gradient managing device that flexibly manages a temperature coefficient of the reference voltage,
the constant voltage source having:
a constant current circuit including a plurality of constant current paths that include a first current path having a first resistance being interposed therein, and the band gap circuit formed from a pair of transistors in a current mirror configuration that are interposed in the plurality of constant current paths, respectively; and
a second constant current path that is connected in cascade to the constant current circuit, formed in a multiple-current mirror configuration and has a second resistance interposed therein,
the temperature gradient managing device that flexibly selects a ratio of the second resistance with respect to the first resistance based on a predetermined formula relating to a size ratio of the pair of transistors,
at least one of the first resistance and the second resistance of the constant voltage source being composed of a multiple-stage switching type variable resistance that flexibly sets an optional resistance value with transistor switches that ON-OFF operate according to data stored in a non-volatile memory, and
an offset adjust mode that temporarily sets at least one of a load resistance of the voltage follower circuit and the second resistance to a minimum value.
3. The temperature characteristic compensation apparatus according to claim 1 , the temperature characteristic compensation apparatus being formed in combination with a microcomputer, the constant current paths including the first constant current path for operating the band-gap circuit being supplied with power from a constant voltage stabilized power supply provided within the microcomputer.
4. The temperature characteristic compensation apparatus according to claim 1 , comprising an offset adjust mode that temporarily sets at least one of a load resistance of the voltage follower circuit and the second resistance to a minimum value.