AD822 Dual Operational Amplifier High-Precision Low-Power Rail-to-Rail Output Operational Amplifier

Introduction

The AD822 is a dual precision, low power FET input op ampthat can operate from a single supply of 5 V to 30 V or fromdual supplies of ±2.5 V to ±15 V. It has true single-supply capabilitywith an input voltage range extending below the negative rail,allowing the AD822 to accommodate input signals below groundwhile in the single-supply mode. Output voltage swing extendsto within 10 mV of each rail, providing the maximum outputdynamic range.
The FET input structure of the AD822 makes it highly suitable for high-impedance sources. It also features low offset voltage and low drift. This article will focus on the characteristics, advantages, application scenarios, and basic parameter information of the AD822.

FEATURES

• True single-supply operation
• Output swings rail-to-rail
• Input voltage range extends below ground
• Single-supply capability from 5 V to 30 V
• Dual-supply capability from ±2.5 V to ±15 V
• High load drive
• Capacitive load drive of 350 pF, G = +1
• Minimum output current of 15 mA
• Excellent ac performance for low power
• 800 µA maximum quiescent current per amplifier
• Unity-gain bandwidth: 1.8 MHz
• Slew rate of 3 V/μs
• Good dc performance
• 800 µV maximum input offset voltage
• 2 µV/°C typical offset voltage drift
• 25 pA maximum input bias current
• Low noise
• 13 nV/√Hz at 10 kHz
• No phase inversion

Advantages

1. The input bias current is extremely low (< 25 pA).
The FET input structure makes it highly suitable for high-impedance sources such as photoelectric sensors, electrochemical probes, pressure sensors, etc., ensuring measurement accuracy.
2. Low offset voltage and low drift
Offset voltage: ≤ 800 µV
Temperature drift: ≈ 2 µV/°C
It can maintain high accuracy even under long-term use or temperature variations.
3. True single power supply operation capability
The input range can be lower than the negative power rail (below 0 V), which is very suitable for single-power supply acquisition systems, reducing the complexity of additional circuit design.
4. Output swing close to the power rail (only 10 mV difference)
It can maximize the dynamic range and improve the performance of the signal chain, which is very suitable for low-voltage or battery-powered devices.
5. Wide power supply range, adaptable
Single power supply: 5 V～30 V
Dual power supply: ±2.5 V～±15 V
Compatible with various system designs in industrial, medical, and portable applications.
6. Low power consumption (800 µA per amplifier)
Suitable for battery-powered, portable devices, low-power instruments, etc.
7. Good AC performance
1.8 MHz unit gain bandwidth
3 V/µs conversion rate
–93 dB THD (10 kHz)
It performs stably and has low distortion in scenarios such as audio, signal conditioning, and circuit buffering.
8. Dual-channel design, saving space and cost
An integrated two-precision operational amplifier in one package, suitable for multi-channel signal processing, improving PCB layout efficiency

APPLICATIONS

Battery-powered precision instrumentation
The AD822 consumes only 800 µA and features a wide supply voltage range and nearly rail-to-rail output, making it ideal for portable or battery-powered measurement devices.
Photodiode preamps
The output current of the photodiode is extremely small, and usually a high input impedance amplifier is required to convert and amplify the signal.
Active filters
The low distortion and sufficient bandwidth of AD822 make it suitable for the fabrication of high-performance filters.
12-bit to 14-bit data acquisition systems
During data acquisition, the front-end amplifier requires high precision and low noise to match the accuracy of the ADC.
Medical instrumentation

Medical signals are usually very weak and require high levels of resistance to noise and stability.
Low power references and regulators
In voltage stabilization or reference circuits, operational amplifiers are commonly used for error amplification or buffering functions.

Applications information

Input Characteristics

High input impedance & low bias current
Using an N-channel JFET input stage, it offers extremely high input impedance and picohenry-level input current, suitable for high-impedance sensors.
Wide input common-mode range
The input voltage can be lower than 0.2 V below the negative power supply rail and can operate within a range 1 V lower than the positive power supply, suitable for single power supply and weak signal acquisition.
No phase inversion design
The input voltage can remain stable even when it reaches +VS; it can be further protected by a series resistor when exceeding the power supply voltage.
Strong input overvoltage protection capability
When connected in series with a 1 kΩ resistor, it can withstand up to 10 V of continuous overvoltage; inputs lower than –VS can be safely sustained up to –20 V under certain conditions.
Excellent low-noise performance
Wideband noise is only 13 nV/√Hz, and remains stable at low frequencies; for applications with **>10 kΩ source impedance and >1 kHz bandwidth**, it hardly increases system noise.

Output Characteristics

1. High rail-to-rail output capability: The output can approach negative power supply at 5 mV and positive power supply at 10 mV, providing the maximum dynamic range.
2. Good driving capability: The typical output saturation resistance is 40 Ω (source current) / 20 Ω (sink current), which can easily drive medium loads.
3. High precision retention: When the load exceeds 20 kΩ, the output will only affect the input error within 180 mV from the power rail, and the accuracy is stable.
4. Fast overdrive recovery: After the output enters saturation, it can return to the normal linear working state within approximately 2 μs when the input recovers.
5. Strong compatibility with capacitive loads: It can stably drive medium-capacitance loads; the unity gain follower still remains stable when driving approximately 350 pF.

Absolute maximum ratings

OUTLINE DIMENSIONS

Conclusion

The AD822 is a low-power, high-precision dual operational amplifier that offers a wide power supply voltage range, low input bias current, and low noise performance. It is highly suitable for precise applications that require both signal integrity and low power consumption. Its rail-to-rail output and excellent gain bandwidth enable it to perform stably and reliably in battery-powered devices, medical testing, photoelectric front ends, data acquisition systems, and active filters. The AD822 combines high cost-effectiveness and versatility, making it the preferred component for analog signal conditioning, voltage/current amplification, and sensor interfaces.