### Technical Overview: AD8422ACPZ-R7 The **AD8422ACPZ-R7** is a high-precision, low-power, 3-op-amp instrumentation amplifier manufactured by **Analog Devices**. It is designed to extract small differential signals in the presence of large common-mode noise. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Architecture** | 3-Op-Amp Instrumentation Amplifier | | **Gain Range** | 1 to 1000 (Set by a single external resistor $R_G$) | | **Supply Voltage** | Dual: ±2.3V to ±18V | Single: 4.6V to 36V | | **Quiescent Current** | 330 µA (Max) | | **Input Offset Voltage** | 60 µV (Max) | | **Common-Mode Rejection Ratio (CMRR)** | 94 dB (Minimum, G=1) | | **Bandwidth** | 2.2 MHz (G=1) | | **Package Type** | 16-Lead LFCSP (Lead Frame Chip Scale Package) | --- ### 2. Core Functional Components The internal electronic structure consists of three main stages that define its performance: #### A. Input Stage (Pre-Amplifier) The device uses a high-impedance input stage consisting of two operational amplifiers. * **High Input Impedance:** Minimizes loading effects on sensitive sensors. * **EMI Filtering:** The AD8422 includes internal RFI (Radio Frequency Interference) filters to prevent high-frequency noise from rectifying as DC errors. #### B. Gain Setting ($R_G$) The gain is determined by a single external resistor connected between pins 1 and 8. The formula for the gain $G$ is: $$G = 1 + \frac{19.8 \text{ k}\Omega}{R_G}$$ #### C. Output Stage (Difference Amplifier) The third op-amp functions as a subtractor, removing the common-mode voltage and providing the amplified differential signal. It includes a **Reference Pin (REF)** which allows the output to be offset to a specific voltage (e.g., mid-supply). --- ### 3. Electronic Performance Features * **Low Power Consumption:** At only 330 µA maximum supply current, it is ideal for battery-powered industrial and medical devices. * **Precision Performance:** It features very low input bias current (typically 0.5 nA) and low offset drift ($0.3 \mu V/^\circ C$), ensuring accuracy over temperature changes. * **Robustness:** The inputs are protected against Overvoltage (ESD) and can withstand voltages beyond the power supply rails (up to 40V from the opposite rail). --- ### 4. Typical Applications The AD8422 is commonly used in circuits requiring high precision and low power: 1. **Medical Instrumentation:** ECG and non-invasive blood pressure monitors. 2. **Industrial Process Control:** Bridge amplifiers for strain gauges and pressure sensors. 3. **Data Acquisition:** Interfacing low-voltage sensors to high-resolution ADCs. ---