## Overview of AD8421ACPZ-R7 The **AD8421ACPZ-R7** is a high-performance, low-power, extremely low-noise instrumentation amplifier designed by Analog Devices. It is specifically engineered to deliver high precision for data acquisition and signal conditioning applications. --- ### 1. Key Technical Specifications The following table summarizes the primary electrical characteristics of the AD8421 series: | Parameter | Value / Range | | :--- | :--- | | **Gain Range** | 1 to 10,000 (Set by a single resistor) | | **Input Voltage Noise** | 3.2 nV/√Hz @ 1 kHz | | **Bandwidth** | 10 MHz (G = 1), 2 MHz (G = 100) | | **Common-Mode Rejection Ratio (CMRR)** | 94 dB (Minimum, G = 1) | | **Slew Rate** | 35 V/µs | | **Quiescent Current** | 2.3 mA (Maximum) | | **Supply Voltage Range** | ±2.5 V to ±18 V | | **Package Type** | LFCSP-16 (Lead Frame Chip Scale Package) | --- ### 2. Functional Description The AD8421 utilizes a classic **three-op-amp architecture**. This configuration allows it to extract small differential signals in the presence of large common-mode voltages. #### A. Gain Setting The gain ($G$) is determined by an external resistor, $R_G$. The relationship is defined by the following formula: ```text G = 1 + (9.9 kΩ / RG) ``` #### B. High Speed and Precision Unlike many high-precision instrumentation amplifiers that trade speed for accuracy, the AD8421 offers a high slew rate (35 V/µs) and wide bandwidth. This makes it ideal for multiplexed applications where fast settling times are required. --- ### 3. Pin Configuration (LFCSP-16) The "ACPZ" suffix denotes the 16-lead LFCSP package, which provides excellent thermal performance and a small footprint. | Pin Number | Mnemonic | Description | | :--- | :--- | :--- | | 1, 4, 13, 16 | NC | No Internal Connection | | 2 | -IN | Negative Input | | 3 | +IN | Positive Input | | 5, 12 | RG | Gain Setting Resistor Pins | | 8 | -Vs | Negative Supply Voltage | | 9 | REF | Reference Pin (Sets Output Offset) | | 10 | VOUT | Output Terminal | | 11 | +Vs | Positive Supply Voltage | --- ### 4. Typical Applications * **Medical Instrumentation:** ECG and EEG monitoring due to low noise. * **Industrial Process Control:** Bridge amplifiers for pressure and temperature sensors. * **Data Acquisition:** High-speed, high-resolution ADC driving. * **Precision Signal Conditioning:** In environments with high electromagnetic interference. --- ### 5. Part Number Breakdown * **AD8421:** Base Model Number. * **A:** Performance Grade (Standard). * **CP:** Lead Frame Chip Scale Package (LFCSP). * **Z:** RoHS Compliant (Lead-free). * **R7:** 7-inch Tape and Reel packaging (typically 1,500 units).