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# Temperature compensating of electric circuit

All parts change the value depending on the temperature. There is a thing that it is not necessary to think about the temperature so much in designing a circuit like resistance, and is a thing that the characteristic cannot be separated from the temperature like the semiconductor. What is the thing to have to put the circuit design, especially the nature?

## Examples of temperature and temperature compensation diodes

The voltage of the directions of easy flow between base emitters of a general silicon diode and the transistor has the voltage descent of about 0.6-0.7V. Moreover, this temperature property is C.

The temperature property of a general Zenner diode has the thing of about 5V and it has a big, positive temperature property by rising of the voltage in Sakai more than it.

It is a method of use often that connects the diode with a negative temperature property in the temperature compensating of the Zenner diode with a positive temperature property from this with the series. If it is insufficient, it makes it to 2 pieces 3 pieces and the series with one diode. In this case, it is necessary to consider going up of about 0.6-0.7V voltage per with one diode made a series.

Moreover, it is a method of the use often for making the Zenner diode of 5-6V a series to improve the temperature property.

## Transistor temperature compensation cases

The temperature property of the transistor has a negative temperature property as well as the diode between base emitters. Therefore, it is easy for the forward voltage between base emitters to become small if it rises in temperature, and to cause the runaway effect when the bias is added to the base only by the resistance division.
The technique for putting resistance in the emitter to prevent this and multiplying the direct current negative feedback is general. In addition, it is a method of using the technique for putting the diode in the series, joining the diode and the transistor to the resistance between the base and the earth in addition so that it may make amends for the temperature, and making it at the same temperature very often.

It is a method of use often in IC that the circuit is made a differential amplifier that doesn't receive the temperature influence easily, and runs away from the problem of the temperature.

A general thermistor has a negative temperature property it is a method that often uses in the temperature compensating of the entire circuit though there is a method of making amends for the temperature by using this, too.

## LC resonant circuit temperature compensation cases

In the LC resonant circuit in the oscillation circuit etc. , the coil generally has a positive temperature property. If the temperature property of the capacitor is 0, it becomes a positive temperature property in the entire circuit. Because various things are made as for the temperature property of the capacitor, it is general to use the thing of a negative temperature property to deny the temperature property of the coil.

Because the oscillatory frequency is not decided only by the value of LC with the outside in the oscillation circuit, it is general that the circuit is made a circuit with steady frequency, the temperature property of the entire circuit is measured, and it makes amends for the temperature. Moreover, it is a method of often using that the entire circuit is put in the temperature controlled bath.

## Temperature compensation of temperature characteristics for cases of electrolytic capacitors

The electrolytic capacitor is one of the parts that the temperature property is very bad. The electric conductance changes greatly depending on the temperature because the viscosity of the electrobath used for the aluminum electrolytic capacitor depends at the temperature. Especially, the electric conductance decreases, equivalent series resistance (ESR) increases, and the electrostatic capacity decreases greatly for the low temperature.

There might be a problem when capacity is enlarged though it is general to use the electrolytic capacitor of very large capacity in consideration of the decrease in this temperature. For this case, there is a hand that doesn't use the electrolytic capacitor either.

The symptom that becomes a problem due to the decrease in the temperature might be suppressed when the electrolytic capacitor is used by all means and the symptom be suppressed by using the thermistor etc. for the electric circuit. The showing place of design engineer's idea around here.