Thermistor-Based Temperature Compensation Circuits

Key Takeaways

• Temperature compensation circuits are used to compensate for the effects of temperature on the electrical quantity of interest in the circuit.

• Thermistors are resistors that are highly sensitive to temperature. 

• In temperature compensation circuits, thermistors can be used either in active or passive configurations.

High temperatures are almost never a good thing when it comes to electronics; most electronic failures and poor performances are caused by elevated temperatures. In sensitive circuits, taking countermeasures against the thermal influence on circuit performance is recommended to mitigate these issues.

One way designers reduce thermal effects on circuits is by using a temperature compensation circuit. Temperature compensation circuits are used to compensate for the effects of temperature on the electrical quantity of interest in a circuit. In this article, we will discuss one type of temperature compensation circuit, the thermistor-based temperature compensation circuit, but first, let’s take a look at the negative effects temperature can have on electronic circuit performance to understand why we need these circuits in the first place.

The Effects of Temperature on Electronic Circuit Performance

Circuit parameters, characteristics, and performance undergo changes with thermal effects. Here are some examples of ways in which temperature affects resistors, integrated circuits, and semiconductor devices.

Resistors

With an increase in temperature, it is common to see degradation in the performance of electronic devices. This is due to the change in component values with temperature. For example, the temperature effects on resistors result in resistance value changes or errors and variations in output quantities. Sometimes high temperatures may end up in resistor failure modes such as electrical open circuit conditions.

Integrated Circuits

In integrated circuits, thermal effects can completely jeopardize the purpose of the chip. In certain cases, over-temperature protection is activated in ICs and shuts down chip operation. Otherwise, high temperatures can cause other ill effects in ICs such as altering the switching speeds, unintended operations, unexpected behaviors, or the misinterpretation of critical inputs. In some cases, high temperatures are capable of burning off the IC itself. 

Semiconductor Devices

In solid-state electronics, the temperature can cause intense heat in semiconductor junctions. If semiconductor devices are not well protected against repeated temperature increases, they can suffer from a phenomenon called thermal runaway, which damages devices.

Considering all the above-mentioned effects of temperature on electronic circuit performance, it is important to incorporate temperature compensation circuits. The upcoming section discusses the thermistors used in temperature compensation circuits. 

Thermistors in Temperature Compensation Circuits 

A temperature compensation circuit is a method used in electronic circuits to counteract temperature variations. It enables the circuit to adjust its performance so that the effect of temperature is corrected. Generally, temperature sensors are a big part of temperature compensation circuits. Among the various temperature sensors, the thermistor is the most frequently seen element in temperature compensation circuits.

Thermistors are resistors that are highly sensitive to temperature. They have either a negative or positive temperature coefficient of resistance. In negative temperature coefficient (NTC) thermistors, the resistance increases with a decrease in temperature and vice versa. They sense temperature changes and enable the compensation to nullify the thermal effects.

In temperature compensation circuits, thermistors can be used either in active or passive configurations. In active configurations, thermistors act as sensors that enable the operation of compensation circuits to bring the temperature effects under control. In passive configurations, thermistors offset the circuit resistance-temperature characteristics by their own characteristics and flatten the overall resistance-temperature graph.            

Applying Thermistor-Based Temperature Compensation Circuits

Thermistor-based temperature compensation circuits are used in:

• Electronic circuits
• Measurements of instruments and meters
• Computational devices
• Solenoids and winding coils in instrumentation systems
• Amplifiers and oscillators
• Integrated circuits
• Control systems

Thermistor-based temperature compensation circuits are effective at nullifying thermal effects on electronic circuit performance. Cadence software, like the Celsius Thermal Solver featured in the video below, offers thermal analysis tools, which help designers understand how circuits perform under elevated temperatures.

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