Thermistor Signal Amplifier for Temperature Control

The INA330 is a precision amplifier designed for thermoelectric cooler (TEC) control in optical networking applications. It is optimized for use in 10k thermistor-based temperature controllers. The INA330 provides thermistor excitation and generates an output voltage proportional to the difference in resistances applied to the inputs. It uses only one precision resistor plus the thermistor, thus providing an alternative to the traditional bridge circuit. This new topology eliminates the need for two precision resistors while maintaining excellent accuracy for temperature control applications.

An excitation voltage is applied to the thermistor (RTHERM) and precision resistor (RSET), creating currents I1 and I2. The current conveyor circuit produces an output current, I0, equal to I1 – I2, which flows through the external gain-setting resistor. A buffered voltage output proportional to I0 is also provided.

The INA330 offers excellent long-term stability, and very low 1/f noise throughout the life of the product. The low offset results in a 0.009°C temperature error from –40°C to +85°C. It comes in MSOP-10 packaging and operates with supply voltages from +2.7V to +5.5V. It is specified over the industrial temperature range, –40°C to +85°C, with operation from –40°C to +125°C.