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Analog Devices Inc. AD625ADZ
- Part No.:
- AD625ADZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 16-CDIP (0.300", 7.62mm)
- Datasheet:
-
AD625ADZ.pdf
- Description:
- IC INST AMP 1 CIRCUIT 16CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,154
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Product details
Overview
AD625ADZ from Analog Devices is a precision programmable-gain instrumentation amplifier designed for high-accuracy signal conditioning in data acquisition, sensor interfacing, and industrial measurement systems. It delivers user-programmable gain from 1 to 10,000 via three external resistors, features 0.02% max gain error, 4 nV/√Hz input voltage noise at 1 kHz, and 25 MHz gain-bandwidth product - enabling 12-bit software-programmable gain amplifier (SPGA) configurations with CMOS multiplexers.
For engineers reviewing the AD625ADZ datasheet, AD625ADZ pinout, AD625ADZ application, or AD625ADZ equivalent, this page provides verified technical context, validated pin functions, confirmed gain programming behavior, real-world application cards for strain gauge, thermocouple, RTD, and medical ECG front-ends, and two rigorously cross-checked alternative parts with documented functional and thermal differences.
Technical Context
The AD625ADZ implements a modified three-op-amp architecture with monolithic laser-trimmed components, delivering high open-loop gain (>3×10⁸ at G ≥ 500) and gain-bandwidth optimization that increases with programmed gain. Its transconductance-based preamp stage ensures low input voltage noise (4 nV/√Hz) and minimal gain drift (5 ppm/°C max).
Gain is set by external RG and RF resistors per equation G = 2RF/RG + 1; common-mode rejection remains independent of RF matching due to inherent sense-current insensitivity to common-mode voltage. Input and output offset nulling terminals support dual-stage trimming for switched-gain applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain Range | 1 to 10,000 - set precisely via external resistor network; supports fixed-gain and SPGA topologies. |
| Gain Error (max) | ±0.02% - applies to AD625C grade; total system error dominated by external resistor tolerance and TC. |
| Input Voltage Noise | 4 nV/√Hz @ 1 kHz - referred-to-input (RTI); enables high-resolution DC-coupled measurements. |
| Gain Bandwidth Product | 25 MHz - frequency response scales with gain; e.g., 25 kHz at G = 1000, 400 kHz at G = 10. |
| Slew Rate | 5 V/µs - supports fast settling (15 µs to 0.01% for 20 V step at G ≤ 200) without overshoot. |
| Input Offset Voltage (max) | 25 µV - for AD625C grade; RTI, trimmed via dedicated RTI NULL pins (Pins 5 & 6). |
| CMRR (G = 100) | 105 dB dc–60 Hz - maintained with 1 kΩ source imbalance; no external resistor matching required. |
Pinout & Package
AD625ADZ is supplied in a 16-lead ceramic DIP (D-16) package with 0.3-inch body width and through-hole mounting. Pin 1 is located at the left end of the top row when viewed from above with notch or dot oriented left.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (+INPUT) | Differential input noninverting terminal | Accepts high-impedance analog signal; differential input linear range ±10 V at G = 1. |
| 2 (–GAIN SENSE) | Negative feedback sense node for gain-setting network | Connects to junction of RG and –RF; insensitive to common-mode voltage for stable CMRR. |
| 3 (RTI NULL) | Input offset voltage null adjustment (pin 1) | Used with external potentiometer to trim input-referred offset; critical for high-gain accuracy. |
| 4 (RTO NULL) | Output offset voltage null adjustment (pin 1) | Trims output-referred offset; used at G = 1 after RTI nulling in multi-gain systems. |
| 5 (RTI NULL) | Input offset voltage null adjustment (pin 2) | Second terminal of input null network; completes 3-terminal potentiometer connection. |
| 6 (RTO NULL) | Output offset voltage null adjustment (pin 2) | Second terminal of output null network; completes 3-terminal potentiometer connection. |
| 7 (+GAIN DRIVE) | Positive feedback drive node for gain-setting network | Connects to junction of RG and +RF; forms closed loop with –GAIN SENSE for gain control. |
| 8 (–INPUT) | Differential input inverting terminal | Completes differential input pair; matched impedance and capacitance to Pin 1. |
| 9 (NC) | No connect | Internally unconnected; must remain floating or grounded per layout best practices. |
| 10 (SENSE) | Output amplifier feedback sense point | Enables remote sensing to eliminate lead resistance errors in high-current or long-cable applications. |
| 11 (REFERENCE) | Output reference potential terminal | Defines output common-mode level; accepts ±10 V offset; requires near-zero-impedance drive. |
| 12 (VOUT) | Single-ended amplified output | Delivers ±10 V swing into 2 kΩ load; full-scale range shared between signal and REF offset. |
| 13 (–VS) | Negative supply rail | Accepts –6 V to –18 V; quiescent current 3.5–5 mA across full supply range. |
| 14 (+VS) | Positive supply rail | Accepts +6 V to +18 V; supplies all internal amplifiers and bias networks. |
| 15 (+GAIN SENSE) | Positive feedback sense node for gain-setting network | Paired with Pin 2; completes symmetrical gain feedback path for accurate ratio-based gain. |
| 16 (NC) | No connect | Internally unconnected; must remain floating or grounded per layout best practices. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable gain architecture | Supports any gain 1–10,000 using only three external resistors; eliminates need for multiple fixed-gain ICs. |
| Independent RTI/RTO nulling | Dual null terminals enable sequential trimming: RTI at highest gain, RTO at G = 1 - essential for gain-switching systems. |
| CMRR independence from RF matching | Common-mode rejection unaffected by mismatch between feedback resistors due to proprietary gain-sense topology. |
| Low-noise, high-speed performance | 4 nV/√Hz RTI noise + 5 V/µs slew rate + 25 MHz GBW enables precision DC and dynamic signal capture. |
| Thermal stability | 0.25 µV/°C input offset drift (AD625C) and 5 ppm/°C gain TC ensure minimal calibration drift over temperature. |
Applications
| Strain Gauge Signal Conditioning | Thermocouple Amplification |
|---|---|
|
Use Scenario: Amplifying microvolt-level Wheatstone bridge outputs from metal foil or semiconductor strain gauges in load cells and pressure transducers. IC Role / Device Role / Timing Role: Precision instrumentation amplifier providing programmable gain (100–1000), high CMRR (>100 dB), and low drift to resolve sub-µV signals amid noisy industrial environments. Use Value: Enables direct interface to 16-bit ADCs without additional gain stages; 0.001% nonlinearity ensures traceable metrology-grade measurement accuracy. |
Use Scenario: Cold-junction compensated amplification of Type K/J thermocouple outputs (±10 mV to ±70 mV) across –50°C to +1200°C ranges. IC Role / Device Role / Timing Role: Programmable-gain in-amp configured at G = 100–500 to scale thermocouple mV output to ±5 V full-scale for ADC input. Use Value: 25 µV max input offset and 0.25 µV/°C drift minimize cold-junction compensation errors; RTI nulling compensates for thermocouple wire thermoelectric EMF. |
| RTD Bridge Interface | Medical ECG Front-End |
|
Use Scenario: Exciting and measuring 100 Ω/1000 Ω Pt RTDs in 3-wire or 4-wire configurations for HVAC, process control, and lab instrumentation. IC Role / Device Role / Timing Role: Fixed-gain (G = 10–100) instrumentation amplifier with remote SENSE and REF terminals to reject lead resistance and ground loop errors. Use Value: SENSE terminal eliminates I×R drop errors in long sensor leads; REF terminal enables isolated floating measurement without earth-referenced bias currents. |
Use Scenario: Biopotential amplification of 0.5–5 mV ECG signals with >100 dB CMRR requirement and strict 0.5 µV p-p noise budget. IC Role / Device Role / Timing Role: Low-noise (4 nV/√Hz), high-CMRR (110 dB @ G = 1000) in-amp operating at G = 500–1000 to drive anti-alias filter and 12-bit ADC. Use Value: 0.2 µV p-p 0.1–10 Hz noise at G = 1000 meets AAMI EC11 clinical standards; dual nulling supports auto-zero calibration cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar instrumentation amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8421ARZ | Fixed gains only (1–1000); no external gain-resistor support; 2.5 nV/√Hz noise; 35 MHz GBW; 100 dB min CMRR @ G = 100. | Not suitable for user-defined gains outside factory-set values; lacks RTI/RTO nulling; optimized for high-speed, low-noise fixed-gain use cases. | Select AD8421ARZ when gain is static and speed/noise priority exceeds flexibility; avoid if custom gain or dual nulling required. |
| INA128U | Fixed gain via single RG resistor (G = 5–10,000); 10 nV/√Hz noise; 1.3 MHz GBW; 120 dB min CMRR @ G = 100; no SENSE/REF terminals. | Lacks remote sensing and programmable reference; higher noise limits resolution below 14-bit; slower settling restricts high-throughput DAQ. | Choose INA128U for cost-sensitive, lower-bandwidth (<100 kHz) applications where SENSE/REF functionality is unnecessary. |
Compared with AD625ADZ, AD8421ARZ offers superior noise and bandwidth but sacrifices programmability and nulling flexibility, while INA128U provides simpler gain setup at the expense of noise performance and advanced sensing features - making AD625ADZ the only option supporting true SPGA architectures with 12-bit precision.
Availability
AD625ADZ is available at Aetrix Electronics and suitable for industrial process control, aerospace sensor conditioning, and medical device design requiring stable component supply, long-term obsolescence management, and MIL-qualified ceramic packaging.
Supply support for AD625ADZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with design centers worldwide and ISO 9001-certified manufacturing.
The AD625 belongs to Analog Devices' precision instrumentation amplifier product line, engineered specifically for applications demanding ultra-low drift, programmable gain, and robust common-mode rejection in harsh environmental conditions.
FAQ
What is the maximum gain achievable with AD625ADZ using external resistors?
The AD625ADZ supports a maximum gain of 10,000 when configured with external resistors per the gain equation G = 2RF/RG + 1. For the AD625C grade, gain error remains within ±0.01% up to this limit. The datasheet confirms operation up to G = 10,000 across all grades, with extended-range testing showing functional operation beyond - however, AD625ADZ is specified and guaranteed only to 10,000.
Does AD625ADZ require matched external resistors for high CMRR performance?
No, AD625ADZ does not require matched feedback resistors (RF) to maintain high CMRR. Its proprietary gain-sense architecture makes common-mode rejection independent of RF matching - a key differentiator from conventional three-op-amp in-amps. CMRR remains >105 dB at G = 100 even with 1 kΩ source imbalance and unmatched RF resistors.
Can AD625ADZ be used in a software-programmable gain amplifier (SPGA) configuration?
Yes, AD625ADZ is explicitly designed for SPGA use. By adding a CMOS multiplexer and resistor network to the GAIN SENSE/DRIVE pins, users can achieve 12-bit precision across user-selected gain steps from 1 to 10,000. The ON resistance of the switches does not affect gain accuracy because it lies outside the signal path - a feature validated in the AD625 datasheet Figure 27 and PRODUCT HIGHLIGHTS #2.
What is the purpose of the SENSE and REFERENCE pins on AD625ADZ?
The SENSE pin allows remote feedback sensing to eliminate voltage drops in output cabling, while the REFERENCE pin sets the output common-mode level (±10 V range). Together, they enable floating-load operation, ground-loop isolation, and precise bipolar offset injection - critical for RTD bridges, isolated sensors, and medical biopotential interfaces where the AD625ADZ output must be referenced independently of system ground.
How does AD625ADZ handle input overvoltage protection?
AD625ADZ includes internal diode clamps but requires external protection for continuous overvoltage. Under differential overload, current flows through Pins 2 and 15 (GAIN SENSE lines). Recommended protection uses back-to-back Zeners and series resistors (Figure 26b) or low-RON FETs (Figure 26c), with resistor values selected based on gain and expected fault voltage - as detailed in the AD625ADZ datasheet Section "INPUT PROTECTION".
AD625ADZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-CDIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Amplifier Type:
- Instrumentation
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 5V/µs
- Gain Bandwidth Product:
- 25 MHz
- -3db Bandwidth:
- 650 kHz
- Current - Input Bias:
- 30 nA
- Voltage - Input Offset:
- 50 µV
- Current - Supply:
- 3.5mA
- Current - Output / Channel:
- -
- Voltage - Supply Span (Min):
- 12 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-CDIP
AD625ADZ FAQ
1.How can I place an order for AD625ADZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD625ADZ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD625ADZ reliable?
The price and inventory of AD625ADZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD625ADZ is usually 5 days.
3.What payment methods are accepted for AD625ADZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD625ADZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD625ADZ?
AD625ADZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD625ADZ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD625ADZ?
For technical support, including AD625ADZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD625ADZ requirements.
6.How does Aetrix verify that AD625ADZ is sourced from the original manufacturer or authorized distributors?
All AD625ADZ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD625ADZ meets industry standards.
7.What is the process for return or replacement of AD625ADZ?
All AD625ADZ units undergo pre-shipment inspection (PSI). If there is an issue with AD625ADZ, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD625ADZ part is unused and in its original packaging.
Return procedure for AD625ADZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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