Overview:

The AD8421 is a low-cost, low-power, ultralow-noise, and ultra-low-bias-current high-speed instrumentation amplifier, ideally suited for a wide range of signal conditioning and data acquisition applications. This product features an exceptionally high common-mode rejection ratio (CMRR) that enables the extraction of low-level signals buried in high-frequency common-mode noise across a broad temperature range. With a bandwidth of 10 MHz, a slew rate of 35 V/µs, and a 0.001% settling time of 0.6 µs (G = 10) , the AD8421 is capable of amplifying high-speed signals and excels in applications requiring high-channel-count multiplexed systems. Even at high gains, the current-feedback architecture ensures superior performance. For example, at G = 100, the bandwidth is 2 MHz with a settling time of 0.8 µs. The AD8421 delivers outstanding distortion performance, making it suitable for demanding applications such as vibration analysis. It offers 3 nV/√Hz input voltage noise and 200 fA/√Hz current noise performance, with a quiescent current of only 2 mA, making it ideal for measuring low-level signals. For applications with high source impedance, the AD8421 employs innovative process technology and design techniques to deliver noise performance limited only by the sensor itself. The AD8421 features a unique protection scheme that ensures robust inputs while maintaining extremely low noise. This protection allows inputs to withstand voltages up to 40 V beyond the opposite supply rail without damage. Gain is set from 1 to 10,000 with a single external resistor. The reference pin allows precise offset voltage to be applied to the output. The AD8421 is rated for operation from −40°C to +85°C, with typical performance guaranteed up to 125°C, and is available in 8-lead MSOP and SOIC packages.

Features:

Low Power: Maximum supply current of 2.3 mA

Low Noise:

Maximum input voltage noise of 3.2 nV/√Hz at 1 kHz

Current noise of 200 fA/√Hz at 1 kHz

Excellent AC Performance:

Bandwidth: 10 MHz (G = 1)

Bandwidth: 2 MHz (G = 100)

0.001% settling time: 0.6 µs (G = 10)

CMRR: 80 dB (20 kHz, G = 1)

Slew rate: 35 V/µs

High Precision DC Performance (AD8421BRZ):

CMRR: 94 dB (minimum, G = 1)

Input offset voltage drift: 0.2 µV/°C (maximum)

Maximum gain drift: 1 ppm/°C (G = 1)

Input bias current: 500 pA (maximum)

Input Overvoltage Protection: Withstands up to 40 V beyond the opposite supply rail

Wide Supply Range:

Dual-supply operation: ±2.5 V to ±18 V

Single-supply operation: 5 V to 36 V

Gain Setting: Gain from 1 to 10,000 with a single resistor

Applications:

Medical Instruments

Precision Data Acquisition Systems

Microphone Preamplifiers

Vibration Analysis

Multiplexed Input Applications

ADC Drivers