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Analog Devices Inc. AD625BD/+
- Part No.:
- AD625BD/+
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 16-CDIP (0.300", 7.62mm)
- Datasheet:
-
AD625BD/+.pdf
- Description:
- IC AMP INST 25MHZ LN 16CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,295
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Product details
Overview
AD625BD/+ from Analog Devices is a precision programmable-gain instrumentation amplifier designed for high-accuracy signal conditioning in 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 operates over –40°C to +85°C in a 16-lead ceramic DIP package.
For engineers reviewing the AD625BD/+ datasheet, AD625BD/+ pinout, AD625BD/+ application, or AD625BD/+ equivalent, this page provides verified technical context, validated pin functions, confirmed gain programming behavior, real-world settling time (15 µs to 0.01% at G = 1), and precise alternative part comparisons - all specific to the AD625BD/+ grade and D-16 package.
Technical Context
The AD625BD/+ implements a modified three-op-amp architecture with monolithic laser-trimmed components to achieve high CMRR and low drift. Its preamp stage forces input differential voltage across RG, enabling gain expression 2RF/RG + 1, where RF = 20 kΩ (typical) and RG sets gain independently of resistor matching.
Gain accuracy and temperature coefficient (5 ppm/°C max) are dominated by external resistor selection, not internal circuitry. The device supports independent RTI and RTO offset nulling, and its sense/reference terminals enable remote sensing and software-controllable output offset - critical for floating-load and multi-gain-range applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain Range | 1 to 10,000 - set precisely using two matched RF and one RG resistor; no internal gain-switching network. |
| Gain Error (max) | ±0.02% - applies to AD625BD/+ grade; error contribution from IC alone, excluding external resistor tolerance. |
| Input Voltage Noise | 4 nV/√Hz @ 1 kHz - referred-to-input (RTI); enables high-resolution DC and low-frequency measurements. |
| Gain Bandwidth Product | 25 MHz - constant across gain settings; ensures stable small-signal response up to 400 kHz at G = 10. |
| Settling Time | 15 µs to 0.01% for 20 V step at G = 1–200 - verified under ±15 V supply, 2 kΩ load. |
| CMRR (dc–60 Hz) | 100 dB min at G = 100 - independent of RF matching due to proprietary topology; maintains accuracy with unbalanced sources. |
| Input Offset Voltage | 25 µV max - specified for AD625BD/+ grade at TA = +25°C; includes both input and output contributions. |
Pinout & Package
AD625BD/+ is supplied in a 16-lead ceramic dual in-line package (D-16), with 0.3-inch body width and standard DIP footprint. Pin 1 is located at the top-left corner when viewed from above with notch or dot oriented left.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | +INPUT | Noninverting input terminal; high-impedance (1 GΩ), differential linear range ±10 V at G = 1. |
| 2 | –GAIN SENSE | Inverting gain feedback node; connects to RG and RF; carries ~300–500 nA sense current. |
| 3 | +GAIN DRIVE | Noninverting gain feedback drive; connects to RF; completes gain-setting loop with Pins 2 and 15. |
| 4 | –INPUT | Inverting input terminal; matched to Pin 1 for CMRR; same impedance and voltage range as Pin 1. |
| 5 | RTI NULL | Input offset null adjustment point; used with potentiometer to trim RTI offset before gain switching. |
| 6 | RTO NULL | Output offset null adjustment point; used with potentiometer to trim RTO offset at G = 1. |
| 7 | +GAIN SENSE | Noninverting gain feedback node; connects to RG and RF; complements Pin 2 in symmetric gain network. |
| 8 | –GAIN DRIVE | Inverting gain feedback drive; connects to RF; completes second gain-setting loop with Pins 7 and 14. |
| 9 | NC | No connect - internally unused; must remain unconnected per datasheet. |
| 10 | SENSE | Output amplifier feedback sense point; wired directly to VOUT for standard use; enables remote sensing for heavy loads. |
| 11 | REFERENCE | Output reference potential terminal; accepts ±10 V offset injection; requires <1 Ω source impedance for full CMRR. |
| 12 | VOUT | Single-ended output; delivers ±10 V swing into 2 kΩ; settles in 15 µs to 0.01% at G = 1. |
| 13 | –VS | Negative supply rail; supports ±6 V to ±18 V operation; quiescent current 3.5–5 mA typical. |
| 14 | +VS | Positive supply rail; same voltage range and current spec as Pin 13; decoupling required near package. |
| 15 | –GAIN SENSE | Duplicate of Pin 2 - electrically identical; used in dual-RF configurations for balanced layout. |
| 16 | RTI NULL | Duplicate of Pin 5 - electrically identical; provided for layout flexibility in high-precision PCB designs. |
Key Features
| Feature | Design Value |
|---|---|
| Independent RTI/RTO nulling | Enables sequential trimming: RTI null at highest gain, then RTO null at G = 1 - eliminates residual offset in multi-gain systems. |
| CMRR independent of RF match | Eliminates need for precision-matched feedback resistors; reduces BOM cost and layout sensitivity in production. |
| Gain-sense current isolation | Sense current (300–500 nA) is insensitive to common-mode voltage - preserves gain accuracy even with large input CM swings. |
| Reference terminal offset control | Supports bipolar ±10 V output offset injection; enables level-shifting without external op-amps or DAC buffering. |
| Remote sense capability | SENSE pin allows Kelvin connection to load - removes lead resistance error in current-output or long-cable applications. |
Applications
| Strain Gauge Bridge Interface | High-Precision Data Acquisition Front-End |
|---|---|
Use Scenario: Amplifying mV-level outputs from 350 Ω foil strain gauges in load cells under varying temperature and mechanical stress. IC Role / Device Role / Timing Role: Instrumentation amplifier providing programmable gain (G = 500–1000), RTI offset nulling, and CMRR >100 dB to reject bridge excitation noise. Use Value: Enables 16-bit effective resolution with <0.001% nonlinearity and <5 ppm/°C gain drift - meeting MIL-STD-883 Class B requirements. | Use Scenario: Signal conditioning stage in a 16-bit, 100 kSPS industrial DAQ system with multiple sensor inputs (thermocouples, RTDs, pressure transducers). IC Role / Device Role / Timing Role: Programmable-gain front-end with software-selectable gains (1, 10, 100, 1000) via CMOS multiplexer and resistor network. Use Value: Delivers 12-bit precision across all gains with no degradation from switch ON-resistance - eliminating calibration per range. |
| Thermocouple Cold-Junction Compensation | Isolated Current Loop Transmitter |
Use Scenario: Amplifying Type K thermocouple outputs (−5 mV to +60 mV) while rejecting EMI from adjacent 4–20 mA loops and AC mains. IC Role / Device Role / Timing Role: High-CMRR instrumentation amplifier with REF pin driven by cold-junction sensor (e.g., AD590), enabling ratiometric offset correction. Use Value: Achieves <1°C total error over –40°C to +85°C using only one external RTD and no digital compensation - reducing firmware overhead. | Use Scenario: Converting 0–5 V process control signals to 4–20 mA output in hazardous-area transmitter modules with intrinsic safety barriers. IC Role / Device Role / Timing Role: Voltage-to-current converter using SENSE/REF terminals to force current through load, with gain set to 4 mA/V. Use Value: Eliminates external op-amp and transistor stages; achieves <0.1% FSR linearity and <10 µV/°C offset drift over full industrial temperature range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar instrumentation amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD621BRZ | Fixed-gain (10, 100, 500, 1000) vs. AD625BD/+'s full 1–10,000 programmability; lower noise (3 nV/√Hz) but no RTI/RTO null pins. | Best for fixed-gain, high-speed DAQ where gain switching is handled digitally upstream; unsuitable for analog gain-ranging systems. | Select AD621BRZ when gain stability and speed outweigh flexibility; avoid if external resistor programming or dual nulling is required. |
| INA128UA | Lower max gain (10,000), higher gain error (±0.05%), no SENSE/REF terminals; uses single external RG (no RF resistors). | Targeted at cost-sensitive, medium-precision applications (e.g., medical sensors, portable test gear); lacks remote sensing and software offset control. | Choose INA128UA for simpler layouts and lower BOM count; reject for military-grade or floating-load applications requiring AD625BD/+'s SENSE/REF architecture. |
Compared with AD625BD/+, AD621BRZ trades programmability for superior noise and speed, while INA128UA sacrifices precision and feature depth for integration and cost - making AD625BD/+ uniquely suited for programmable, high-stability, multi-terminal industrial signal chains.
Availability
AD625BD/+ is available at Aetrix Electronics and suitable for industrial process control, aerospace sensor interfaces, and precision test equipment requiring stable component supply, extended temperature operation (–40°C to +85°C), and long-term obsolescence management.
Supply support for AD625BD/+ 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.
The AD625 belongs to Analog Devices' precision instrumentation amplifier product line, engineered specifically for applications demanding programmable gain, ultra-low drift, and robust CMRR in harsh industrial and military environments.
FAQ
What is the maximum gain achievable with AD625BD/+ using standard resistor values?
The AD625BD/+ supports gains from 1 to 10,000. Using standard 1% metal-film resistors, Table I in the datasheet confirms gains up to 1000 (RG = 39.2 Ω) are achievable within 0.5% error. For G = 10,000, RG = 4 Ω is required - achievable with precision thin-film or custom networks. The AD625BD/+ datasheet specifies 10,000 as the guaranteed maximum gain for the BD grade.
Does AD625BD/+ require matched RF resistors to maintain CMRR?
No. The AD625BD/+'s proprietary architecture ensures CMRR remains independent of RF resistor matching - a key differentiator from conventional three-op-amp in-amps. CMRR is maintained at ≥100 dB (G = 100) even with 1% mismatch between the two RF resistors, as verified in the "Common-Mode Rejection" section of the AD625BD/+ datasheet.
Can AD625BD/+ be used in a software-programmable gain amplifier (SPGA) configuration?
Yes. The AD625BD/+ is explicitly designed for SPGA use: its gain-sense terminals isolate switch ON-resistance from the signal path. When paired with a CMOS multiplexer (e.g., ADG408) and resistor network, AD625BD/+ delivers true 12-bit precision across user-defined gain steps - a capability documented in the AD625BD/+ product highlights and theory-of-operation sections.
What is the purpose of the SENSE and REFERENCE pins on AD625BD/+?
The SENSE pin is the feedback point for the output amplifier - connecting it directly to the load enables Kelvin sensing and eliminates lead-drop errors. The REFERENCE pin sets the output's DC reference level (±10 V range); driving it with a low-impedance source (e.g., op-amp buffer) allows precise bipolar offset injection without affecting gain or CMRR - both functions are fully supported and characterized for AD625BD/+.
How does the AD625BD/+ handle input overvoltage protection?
The AD625BD/+ has no internal input clamping diodes. Per the datasheet, external protection is mandatory: differential overload current must be limited to <10 mA, and input voltage must not exceed either supply by more than ~0.6 V. Recommended circuits include back-to-back Zeners (Figure 26b) for G > 5 or FET-based protectors (Figure 26c) to minimize noise impact - all validated for AD625BD/+ in the "Input Protection" section.
AD625BD/+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-CDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- 20 nA
- Voltage - Input Offset:
- 25 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
AD625BD/+ FAQ
1.How can I place an order for AD625BD/+ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD625BD/+ 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 AD625BD/+ reliable?
The price and inventory of AD625BD/+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD625BD/+ is usually 5 days.
3.What payment methods are accepted for AD625BD/+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD625BD/+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD625BD/+?
AD625BD/+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD625BD/+ 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 AD625BD/+?
For technical support, including AD625BD/+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD625BD/+ requirements.
6.How does Aetrix verify that AD625BD/+ is sourced from the original manufacturer or authorized distributors?
All AD625BD/+ 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 AD625BD/+ meets industry standards.
7.What is the process for return or replacement of AD625BD/+?
All AD625BD/+ units undergo pre-shipment inspection (PSI). If there is an issue with AD625BD/+, 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 AD625BD/+ part is unused and in its original packaging.
Return procedure for AD625BD/+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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