Application of the GXSC OPA as a Replacement for the OP2177 in Resistance Temperature Detectors

A resistance temperature detector (RTD) is a temperature sensor that contains a resistor whose resistance value changes with temperature. It is commonly used for temperature measurement in laboratories and industrial processes and offers high accuracy, repeatability, and stability. Signal conditioning operational amplifiers are critical components in RTD temperature measurement systems, directly determining measurement accuracy and system stability. This article recommends the use of the GXSC dual-channel operational amplifier. This device offers excellent DC accuracy, temperature stability, and noise immunity, addressing issues such as weak signal amplification, zero-point drift, and impedance matching in RTD temperature measurement.

The GXSC OPA operates with two independent channels that do not interfere with each other, enabling simultaneous RTD differential signal amplification, reference voltage conditioning, or parallel processing of multiple temperature measurement signals. It is compatible with industrial RTD bridge and differential temperature measurement architectures, featuring extremely low offset voltage and drift, low input bias current, low noise, and low power consumption. 

The GXSC OPA maintains stable output when used with capacitive loads of 1000 pF or higher, requiring no external compensation. At a supply voltage of 30 V, the supply current for each amplifier is less than 500 μA. Its built-in 500 Ω series resistor protects the input signal, allowing the input signal level to exceed the supply voltage by several volts while ensuring no inversion. Applications for these amplifiers include precision diode power measurement, voltage and current level setting, and level detection in optical and wireless transmission systems. Other applications include line-powered portable instruments and control components: signal conditioning for thermocouples, RTDs, strain gauges, and other sensors, as well as precision filters.

The GXSC OPA features are as follows:

• Low offset voltage: 60 μV (maximum)

• Ultra-low offset voltage: 0.7 μV/°C (maximum)

• Low input bias current: 2 nA (maximum)

• Low noise: 8 nV/√Hz (typical)

• Common-Mode Rejection Ratio (CMRR), Power Supply Rejection Ratio (PSRR), and AVO: >120 dB (minimum)

• Low supply current: 400 μA per amplifier

• Dual-supply operation: ±2.5 V to +15 V

• Internal protection circuitry supports input voltages exceeding the supply voltage

• Pin-to-pin replacement for OP2177