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AD623ARZ-RL

Single-supply in-amp, G=1-1000, 200µV Vos, 105dB CMRR, 800kHz BW, rail-to-rail out, SOIC-8, -40~85°C

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Manufacturer Part：

AD623ARZ-RL

Package：

SOIC-8 (R) (4.9 x 3.9 x 1.45 mm, 1.27mm pitch)

Brand：

Product Categories：

Analog Linear ICs, Integrated Circuits ICs

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Description

The AD623ARZ-RL from Analog Devices is a single-supply, rail-to-rail output instrumentation amplifier in an 8-pin SOIC package. It operates from 2.7 V to 12 V single supply (or ±2.5 V to ±6 V dual supply) with only 550 µA max supply current. Gain is set by a single external resistor from 1 (no resistor) to 1000. Key specs include 25 µV typical input offset voltage, 105 dB CMRR at G=100, 800 kHz bandwidth at G=1, 35 nV/√Hz RTI noise at 1 kHz, and 0.1% gain error at G=1. The input common-mode range extends 150 mV below the negative rail. Output swings rail-to-rail. The A-grade specifies 200 µV max Vos and 2 µV/°C max drift. -40°C to +85°C operating range. The -RL suffix denotes 2500-unit tape-and-reel packaging.

Product Introduction:AD623ARZ-RL Product Introduction

The AD623 is an integrated single-supply instrumentation amplifier from Analog Devices that delivers rail-to-rail output swing on a 3 V to 12 V supply. It follows the industry-standard 8-pin in-amp pinout (same as AD620, INA126), making it a drop-in upgrade in many existing designs. The AD623ARZ-RL is the A-grade version in SOIC-8 tape-and-reel packaging with 200-µV max input offset voltage.

The gain is set by a single external resistor according to G = 1 + (100 kΩ/RG). With no external resistor, the device operates at unity gain (G = 1), simplifying PCB layout for applications that do not require amplification. The gain range of 1 to 1000 covers the vast majority of instrumentation applications, from bridge signal conditioning to thermocouple amplification.

The AD623’s key advantage over competing in-amps is its ability to operate from a single 3-V supply while maintaining high CMRR. The CMRR remains stable up to 200 Hz, effectively rejecting power-line harmonics in industrial environments. At G = 10, CMRR is 90 dB minimum at 60 Hz with 1 kΩ source imbalance — sufficient for most sensor applications.

The input common-mode voltage range extends 150 mV below the negative supply rail, enabling the AD623 to amplify signals at or slightly below ground in single-supply systems. This is critical for current-sense applications where the shunt voltage may be near ground.

The rail-to-rail output stage swings to within 10 mV of the supply rails under light load, maximizing dynamic range in low-voltage systems. The 550-µA max supply current is low enough for battery-powered medical instruments and portable data acquisition systems.

The B-grade (AD623BRZ) offers 100-µV max Vos and 1-µV/°C max drift for higher-precision applications at additional cost.

Working Principle:AD623ARZ-RL Working Principle

**Three-Op-Amp Instrumentation Architecture:** The AD623 uses the classic three-op-amp instrumentation amplifier topology: two non-inverting input buffers (A1, A2) and a difference amplifier (A3). The input buffers present high impedance (2 GΩ) to the signal sources and provide gain. The difference amplifier rejects common-mode voltage and extracts the differential signal. The gain resistor RG connects between the RG pins and programs the gain of the input stage.

**Gain Setting Mechanism:** Without RG (RG pins open), the input buffers operate as unity-gain followers, and the overall gain is 1. When RG is connected, the feedback loops of A1 and A2 include RG in their gain paths: G = 1 + (100 kΩ/RG). The internal 100 kΩ resistors are laser-trimmed to 0.01% accuracy, ensuring precise gain.

**Common-Mode Rejection:** The difference amplifier A3 is laser-trimmed for resistor matching, achieving high CMRR. The CMRR increases with gain because the differential signal is amplified by the input stage before reaching A3, while the common-mode voltage is not. At G = 1000, CMRR exceeds 105 dB.

**Rail-to-Rail Output Stage:** The output stage uses a complementary push-pull architecture that can swing to within millivolts of both supply rails. This is essential in 3-V and 5-V single-supply systems where output headroom is limited. The output can drive loads as low as 2 kΩ to the rails.

Pin Description:AD623ARZ-RL Pin Definition and Functions

Pin	Name	Type	Description
1	RG	I	Gain resistor connection; connect external RG between pins 1 and 8; leave open for G=1; G = 1 + (100k/RG)
2	VIN-	I	Inverting input; 2 GΩ input impedance; 25 nA max bias current; common-mode range extends -150mV below negative rail
3	VIN+	I	Non-inverting input; same characteristics as VIN-; differential input voltage up to supply voltage
4	VS-	P	Negative supply; connect to GND for single-supply operation; -2.5V to -6V for dual supply; bypass with 0.1µF
5	REF	I	Reference input; sets output baseline voltage; connect to GND for output referenced to ground; can be used for offset adjustment; 0.35mA max input current
6	VOUT	O	Amplifier output; rail-to-rail swing; VOUT = (VIN+ – VIN-) × G + VREF; can drive 2kΩ loads
7	VS+	P	Positive supply; +2.7V to +12V for single supply; +2.5V to +6V for dual supply; bypass with 0.1µF
8	RG	I	Gain resistor connection; other end of RG; see pin 1

Application Scenarios:In which products and applications isAD623ARZ-RL used

Application	Description
Bridge Sensor Signal Conditioning	Amplify Wheatstone bridge output from strain gauges, load cells, or pressure sensors; G=100-1000 via single resistor; 105dB CMRR rejects bridge common-mode; REF pin offsets output for single-supply ADC; 0.1% gain accuracy at G=1
Current Sense Amplifier	Amplify voltage across current-sense resistor near ground rail; -150mV input range below ground allows low-side sensing; G=10-100 for milliohm shunts; single 5V supply; REF pin sets zero-current baseline to mid-supply for bidirectional sensing
Medical Instrumentation	Amplify ECG/EMG biopotential signals; high CMRR rejects 50/60 Hz common-mode interference; 550µA IQ for battery-powered patient monitors; 25µV Vos minimizes DC error; gain set to 100-500 for microvolt-level signals

Alternative Models:What chips are recommended as replacements for AD623ARZ-RL

Model	Manufacturer	Compatibility	Key Difference
AD623BRZ-RL	ADI	Pin-Compatible Upgrade	Same AD623 in A-grade; 100µV max Vos (vs 200µA); 1µV/°C drift (vs 2µV/°C); higher precision; use for demanding measurement applications
AD8226ARZ	ADI	Pin-Compatible Alternative	Same SOIC-8 in-amp pinout; wider supply range (1.8-11V single); lower Vos (125µV max); 1.5MHz BW; use for wider supply range and higher bandwidth
INA126PA	TI (Burr-Brown)	Functional Equivalent	Single-supply in-amp; SOIC-8; 1.7V-36V supply; 175µA IQ; G=5-10000; use for higher supply voltage applications
INA333AIDR	TI	Competitive Alternative	Zero-drift in-amp; 1.8-5.5V; 25µV max Vos; 0.1µV/°C drift; 350kHz BW; SOIC-8; use for ultra-low drift and lowest supply voltage