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Texas Instruments OPA928DT
- Part No.:
- OPA928DT
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
OPA928DT.pdf
- Description:
- HIGH-VOLTAGE FEMTOAMPERE-INPUT-B
- Quantity:
- Payment:
- Shipping:
Inventory:221
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Product details
Overview
OPA928DT from Texas Instruments is a 36V, femtoampere-input-bias, rail-to-rail input/output precision operational amplifier with e-trim™ technology. It delivers ±5µV input offset voltage, ±0.1µV/°C drift, 2.5MHz gain-bandwidth, 0.07fA/√Hz current noise at 0.1Hz, and integrated high-precision guard buffer - enabling ultra-low-leakage signal conditioning in pH meters and mass spectrometers.
For engineers reviewing the OPA928DT datasheet, OPA928DT pinout, OPA928DT application, or OPA928DT equivalent, key selection criteria include verified 20fA (max) input bias current at 85°C, guard buffer output swing ≤15mV from rail, SOIC-8 low-leakage package layout compatibility, and validated performance across –40°C to +125°C for electrochemical sensor front-ends.
Technical Context
The OPA928DT implements a dual-stage, e-trim™-calibrated architecture that maintains femtoampere-level input bias current across temperature and supply voltage (4.5V–36V), while supporting rail-to-rail common-mode input range and output swing. Its internal guard buffer operates with ±8µV offset and 4.5MHz bandwidth to actively shield high-impedance traces from PCB leakage paths.
This device replaces the OPA128 with improved input bias stability at elevated temperatures and higher supply voltages, and features separate guard (GRD) pins (pins 2 and 7) tied to an internal buffer - not a simple ground connection - enabling active guarding in transimpedance amplifier configurations with photodiodes or ion-selective electrodes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input bias current | 20fA (max) at 85°C, VS = 16V - enables stable DC gain in >1012Ω feedback networks without drift-induced error |
| Input offset voltage | ±5µV (max) - supports sub-µV-level baseline accuracy in coulomb counting and electrometer applications |
| Offset voltage drift | ±0.1µV/°C (max) - ensures <0.5µV total drift over 50°C ambient change, critical for lab-grade instrumentation |
| Unity-gain bandwidth | 2.5MHz - provides sufficient speed for fast settling in high-resolution ADC driver stages |
| Guard buffer BW | 4.5MHz - matches main amplifier bandwidth to prevent phase mismatch in guarded transimpedance circuits |
| Supply range | ±2.25V to ±18V (or 4.5V–36V single) - supports wide dynamic range in portable and mains-powered analyzers |
| Operating temp | –40°C to +125°C - qualified for industrial and field-deployable instrumentation environments |
Pinout & Package
OPA928DT is housed in an industry-standard 8-pin SOIC (D package), 4.9mm × 6mm footprint, optimized for low-leakage PCB layouts with guard ring compatibility and isolated guard trace routing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN+ | Noninverting input | High-impedance node (1000 TΩ || 6 pF) for reference or sensor signal; requires guard trace |
| IN− | Inverting input | Differential input node; used with feedback network in transimpedance or difference amplifier topologies |
| DNC | Do not connect | Pin 3 must remain unconnected and floating - no internal connection or function |
| V− | Negative supply | Lowest potential rail; supports dual-supply operation down to ±2.25V or single-supply as low as 4.5V |
| V+ | Positive supply | Highest potential rail; rated up to ±18V (36V total); powers main amplifier and guard buffer |
| OUT | Output | Rail-to-rail output capable of sourcing/sinking ≥30mA; swings within 5mV of rails under no load |
| GRD (2,7) | Guard buffer output | Two dedicated guard pins driven by internal buffer; must be routed adjacent to IN+ and IN− traces to suppress leakage |
Key Features
| Feature | Design Value |
|---|---|
| e-trim™ calibration | Factory-trimmed input offset and drift eliminate need for external nulling circuitry in precision analog front-ends |
| Integrated guard buffer | Active 4.5MHz buffer drives guard rings around IN+ and IN−, reducing board-level leakage by >10× vs passive guarding |
| Femtoampere input bias | 20fA max at 85°C enables direct interfacing with >1GΩ source impedances without signal corruption |
| Rail-to-rail I/O | Full input common-mode range (V− −0.1V to V+ +0.1V) and output swing to rails support maximum dynamic range in low-voltage systems |
| Ultra-low current noise | 0.07fA/√Hz at 0.1Hz minimizes integration error in long-time-constant measurements like ion chromatography peak detection |
Applications
| pH Meter Front-End | Mass Spectrometer Detector |
|---|---|
Use Scenario: High-impedance glass electrode (108–1010Ω) outputs mV-level signals in aqueous solution monitoring. IC Role / Device Role / Timing Role: Precision transimpedance amplifier with active guarding to reject stray capacitance and humidity-induced leakage. Use Value: 20fA input bias ensures <10nV/min drift over 24h measurement windows, meeting ASTM D1293 pH accuracy requirements. | Use Scenario: Ion current detection from quadrupole or TOF mass analyzer, requiring femtoampere sensitivity and low 1/f noise. IC Role / Device Role / Timing Role: Low-noise current-to-voltage converter with guard-buffered input stage for charge integration. Use Value: 0.07fA/√Hz current noise at 0.1Hz enables sub-femtocoulomb resolution in single-scan acquisition mode. |
| Ion Chromatography (IC) | Lab Electrometer |
Use Scenario: Conductivity cell output during eluent gradient separation, where signal amplitudes range from 100pA to 10nA. IC Role / Device Role / Timing Role: Programmable-gain transimpedance amplifier with selectable feedback resistors and guard-controlled input path. Use Value: ±0.1µV/°C drift guarantees <200pA equivalent input error over 40°C oven temperature ramp, preserving peak area linearity. | Use Scenario: Ultra-high-impedance voltmeter measuring surface potentials or electrophysiological signals with >1014Ω input resistance. IC Role / Device Role / Timing Role: Buffered unity-gain follower with guard-driven input node to isolate meter input from PCB contamination. Use Value: Dual GRD pins (2 & 7) allow symmetrical guard routing, achieving <1fA leakage in Class 100 cleanroom PCB assemblies. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar precision op-amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMP7721MA/NOPB | Higher input bias (3fA typ, 20fA max at 25°C only); no integrated guard buffer; 17MHz GBW | Lacks active guarding - requires external guard driver and careful layout to match OPA928DT leakage performance | Choose when higher bandwidth is prioritized over guaranteed low-leakage layout simplicity |
| ADA4530-1ARZ | Lower input bias (0.1fA typ, 0.6fA max at 25°C); includes guard buffer but only one GRD pin; 2MHz GBW | Superior bias current spec at room temp, but guard architecture less flexible for dual-trace guarding in SOIC layout | Prefer for ultra-low-bias DC-coupled applications below 85°C where guard routing flexibility is secondary |
Compared with LMP7721MA/NOPB and ADA4530-1ARZ, the OPA928DT uniquely combines production-tested 20fA max input bias across –40°C to +85°C, dual GRD pins for robust SOIC guarding, and 2.5MHz bandwidth - making it the only option qualified for field-deployable, wide-temperature electrochemical instruments without layout-dependent performance loss.
Availability
OPA928DT is available at Aetrix Electronics and suitable for pH meter front-ends, mass spectrometer detectors, and ion chromatography systems requiring stable component supply with full traceability and extended temperature qualification.
Supply support for OPA928DT 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
Texas Instruments is a global semiconductor leader delivering analog and embedded processing solutions for industrial, automotive, and communications markets.
The OPA928DT belongs to TI's precision e-trim™ op-amp product line, engineered specifically for ultra-low-leakage, high-impedance signal acquisition in analytical instrumentation and scientific measurement equipment.
FAQ
What is the maximum input bias current specification for OPA928DT over temperature?
The OPA928DT is tested and specified with a maximum input bias current of 20fA at both 25°C and 85°C when VS = 16V, and 75fA at 85°C when VS = 36V. These values are production-tested limits - not typical - ensuring design margin for high-impedance applications like pH sensing and electrometry where leakage directly impacts accuracy.
Does OPA928DT require external guarding, or is the guard buffer sufficient?
The OPA928DT includes an integrated high-precision guard buffer driving pins 2 and 7, eliminating the need for external guard drivers. However, proper PCB layout - including continuous guard rings surrounding IN+ and IN− traces, connected directly to GRD pins - is mandatory to realize the full 20fA input bias performance. The guard buffer alone cannot compensate for poor routing.
Can OPA928DT operate from a single 5V supply?
Yes, OPA928DT supports single-supply operation from 4.5V to 36V. At VS = 5V, it maintains rail-to-rail input (–0.1V to +5.1V common-mode range) and output swing (within 15mV of rails under light load), enabling use in portable battery-powered pH meters and handheld analyzers without dual supplies.
How does the e-trim™ technology in OPA928DT improve long-term stability?
The e-trim™ process uses nonvolatile memory to store factory-calibrated offset and drift coefficients, correcting internal mismatches at wafer test. This results in guaranteed ±5µV input offset and ±0.1µV/°C drift over temperature - significantly tighter than laser-trimmed or post-package trimmed alternatives - reducing system-level calibration frequency in deployed instrumentation.
Is OPA928DT pin-compatible with OPA128?
Yes, OPA928DT is a direct pin-compatible upgrade to OPA128 in the same SOIC-8 (D) package, sharing identical pinout, footprint, and basic functional interface. However, OPA928DT adds dual GRD pins (2 and 7) - both must be used for guarding - whereas OPA128 uses only one guard pin, requiring layout revision to fully exploit the enhanced guarding capability.
OPA928DT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Amplifier Type:
- Standard
- Number of Circuits:
- 1
- Output Type:
- Single Ended, Rail-to-Rail
- Slew Rate:
- 7.5V/µs
- Gain Bandwidth Product:
- 2.5 MHz
- -3db Bandwidth:
- 2.5 MHz
- Current - Input Bias:
- 0.001 pA
- Voltage - Input Offset:
- 10 µV
- Current - Supply:
- 275µA
- Current - Output / Channel:
- 65 mA
- Voltage - Supply Span (Min):
- 4.5 V
- Voltage - Supply Span (Max):
- 16 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
OPA928DT FAQ
1.How can I place an order for OPA928DT through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA928DT 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 OPA928DT reliable?
The price and inventory of OPA928DT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA928DT is usually 5 days.
3.What payment methods are accepted for OPA928DT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA928DT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA928DT?
OPA928DT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA928DT 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 OPA928DT?
For technical support, including OPA928DT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA928DT requirements.
6.How does Aetrix verify that OPA928DT is sourced from the original manufacturer or authorized distributors?
All OPA928DT 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 OPA928DT meets industry standards.
7.What is the process for return or replacement of OPA928DT?
All OPA928DT units undergo pre-shipment inspection (PSI). If there is an issue with OPA928DT, 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 OPA928DT part is unused and in its original packaging.
Return procedure for OPA928DT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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