Part Number: AD8421ARZ

Manufacturer: Analog Devices Inc.


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Technical Specifications of AD8421ARZ

Datasheet  AD8421ARZ datasheet
Category Integrated Circuits (ICs)
Family Linear – Amplifiers – Instrumentation, OP Amps, Buffer Amps
Manufacturer Analog Devices Inc.
Packaging Tube
Part Status Active
Amplifier Type Instrumentation
Number of Circuits 1
Output Type
Slew Rate 35 V/μs
Gain Bandwidth Product
-3db Bandwidth 10MHz
Current – Input Bias 1nA
Voltage – Input Offset 60μV
Current – Supply 2mA
Current – Output / Channel 65mA
Voltage – Supply, Single/Dual (±) 5 V ~ 36 V, ±2.5 V ~ 18 V
Operating Temperature -40°C ~ 85°C
Mounting Type Surface Mount
Package / Case 8-SOIC (0.154″, 3.90mm Width)
Supplier Device Package 8-SOIC

AD8421ARZ-R7 Introduction

Accuracy and dependability are the most important things in signal conditioning and data capture. The AD8421 instrumentation amplifier from Analogue Devices is a device that changes the game. The AD8421 is an important part for many uses because it works quickly, makes very little noise, and is very accurate. In this piece, we look at what the AD8421 can do and how it can help with problems in signal conditioning and data acquisition. We talk about its unique design and impressive performance. We also talk about how well it works for accurate amplification and dealing with noise.

Join us to learn how the AD8421 picks out low-level signals from high-frequency noise, as well as about its amazing bandwidth, settling time, and advanced security features. Check out how it can be used in vibration research, measuring low-level signals, and systems with a lot of channels. With the AD8421, you can open up new possibilities. It helps improve signal conditioning and data acquisition across various domains.

AD8421ARZ-R7 Description

The AD8421 is a flexible and inexpensive instrumentation amplifier that can be used for signal conditioning and data collection. It has very low noise, uses little power, and has a very low bias current. With a high common-mode rejection ratio (CMRR), it can pick up low-level data even when high-frequency common-mode noise is present over a wide range of temperatures.

The AD8421 can boost high-speed signals. It has a bandwidth of 10 MHz, a slew rate of 35 V/s, and a fast settling time of 0.6 s to 0.001% (at a gain of 10). This makes it great for apps with a lot of channels and systems that use multiplexing. Even with higher gains, like G = 100, it still works well, with a 2 MHz frequency and a 0.8 s settling time.

The AD8421 has good distortion performance, which makes it a good choice for uses like vibration analysis that require a lot. It has an input voltage noise of 3 nV/Hz and a current noise of 200 fA/Hz. It uses only 2 mA of idle current. This makes it a great choice for measuring signs that aren’t very strong. It also uses new technology and design methods to make sure that the noise performance is at its best even when the source resistance is high.

The AD8421 has its own ways of protecting itself, so voltages of up to 40 V from the opposite power rail can be put into it without hurting it. It has a gain that can be changed from 1 to 10,000 with a single resistor, making it useful for many different uses. The reference pin can be used to give the output voltage an exact offset. The AD8421 comes in different packages and is designed to work in a wide range of temperatures, so it can be used in a variety of settings.

AD8421ARZ-R7 Features

  • Inputs are safe up to 40 V from the other source.
  • 5 V to 18 V (dual) and 5 V to 36 V (single).
  • Set the gain with just one resistor (G = 1 to 10,000).
  • Available in LFCSP, MSOP, and SOIC with 8 leads each.

AD8421ARZ-R7 Applications

  • Medical equipment
  • Precision data collection
  • Preamplifier the microphone
  • Analysis of vibrations
  • Applications with multiple inputs

Theory of Operation

● Arhitecture

The AD8421 is an amplifier with a three-op-amp design. It has a preamplifier for differential amplification and a difference amplifier to get rid of common-mode voltage. Both the Q1 and Q2 input transistors and the A1 and A2 amplifiers work as current feedback amplifiers. The differential signal is sent to all of the RG pins, which creates a voltage gain between Node 1 and Node 2. The difference amplifier rejects common-mode voltage while keeping the amplified differential voltage. It uses innovations to reduce output mistakes like offset voltage, drift, distortion, and output noise. Laser-trimmed resistors help achieve high accuracy with low gain error and good CMRR that is higher than 94 dB (G = 1). Due to its high-performance pinout and careful design and structure, the AD8421 has a high CMRR performance over a wide range of frequency and temperature. With features like super beta input transistors, bias current compensation, high input impedance, low bias and offset currents, low current and voltage noise, and current-limiting and overvoltage safety, the AD8421 works well even in tough situations.


To get the most out of the AD8421 at the PCB level, it is important to give careful thought to how the board layout is made. The AD8421’s pins are set up in a way that makes sense, which makes this job a lot easier and lets engineers build a layout that makes the device as efficient and useful as possible.

● To control an ADC

Due to its Class AB output stage, low noise and distortion, and high bandwidth and slew rate, the AD8421 is a great choice for driving an ADC in a data acquisition system that needs front-end gain, high CMRR, and dc accuracy. The RC low-pass filter between the AD8421 and the AD7685 has more than one function. It keeps the amplifier output from being overloaded, cuts down on the noise bandwidth, and protects the ADC inputs from overloading. For the best performance, the filter cutoff should be found through experimentation, and the impedance should be greater than 1 k at the highest frequency of the input sound. The gain-of-10 configuration of the AD8421 makes it more sensitive to input data while keeping the SNR loss to a minimum. The ADR435 has a high current output and regulates the load, so the AD7685 can be powered straight from the reference without a separate analogue supply rail. Both the amps and the ADR435 should follow the rules for proper decoupling.

● Trying to figure out how noisy the input stage is

The 3.2 nV/Hz number on this data sheet doesn’t tell the whole story about how noisy the front end of the amplifier is. The source resistance, the voltage noise of the instruments amplifier, and the current noise of the instrumentation amplifier are the three main things that cause noise. In the equations that follow, noise is called the input (RTI). In other words, all noise sources are figured out as if they were at the amplifier’s input. To figure out the noise at the output of the amplifier (RTO), multiply the noise at the input (RTI) by the gain of the instrument amplifier.

Radio Frequency Interference (RFI): When amplifiers are used in situations with strong RF signals, RF correction is often a problem. The problem gets worse if the amplifier needs long wires or PCB traces to connect to the signal source. The noise can look like a dc offset voltage or a train of pulses.


In conclusion, the AD8421 instrumentation amplifier from Analogue Devices is a complete option for signal conditioning and data acquisition. This lets engineers and researchers get accurate measurements and reliable performance. With its unique qualities and advanced features, the AD8421 is a useful part for a wide range of applications. It opens up new options in areas like vibration analysis, low-level signal measurements, and systems with a high channel count.

ICRFQ is the place to go if you want to see how powerful the AD8421 is and start a journey of creativity and learning. Contact ICRFQ right away to get this powerful sensor and find out how it could help your signal shaping and data-gathering projects. With the AD8421 from Analogue Devices, you can take the next step towards making the most of your innovative skills.

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