How to Apply NTC Thermistors 1

NTC components are thermistors with a negative temperature coefficient and are widely used in amateur radio construction. The following primarily covers three key applications:

1) Temperature compensation in instrument circuits  diode

In instrument circuits, there are many components made of metal wires, such as wire-wound resistors. Metal wires generally have a positive temperature coefficient. By using NTC thermistors with a negative temperature coefficient for compensation, the errors caused by temperature changes can be offset. Figure 1 shows a temperature compensation circuit, where the NTC thermistor is connected in parallel with a manganese-copper wire resistor with a very small temperature coefficient, and then in series with the component to be compensated, achieving the temperature compensation effect.

Figure 1 Application of NTC Thermistor in Instrument Temperature Compensation diode

2) TC is used in transistor circuits to stabilize the operating point

Figure 2 shows the circuit for stabilizing the operating point of a transistor using three types of NTC thermistors.

Figure 2(a) shows a simple transistor current amplifier with an NTC thermistor RT connected in the base circuit. When the ambient temperature changes, the output current of the circuit also varies. Adding the NTC allows automatic adjustment of the DC collector current of this stage transistor, stabilizing the output gain of the transistor. diode