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Texas Instruments OPA928DR
- Part No.:
- OPA928DR
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
OPA928DR.pdf
- Description:
- HIGH-VOLTAGE FEMTOAMPERE-INPUT-B
- Quantity:
- Payment:
- Shipping:
Inventory:2,240
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Product details
Overview
OPA928DR 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 high-impedance sensor front-ends such as pH meters and electrometers.
For engineers reviewing the OPA928DR datasheet, OPA928DR pinout, OPA928DR application, or OPA928DR equivalent, this page provides verified specifications, SOIC-8 package layout, real-world use cases in electrochemical instrumentation, and validated alternative options for low-bias-current amplifier selection.
Technical Context
The OPA928DR implements a dual-stage CMOS input stage with e-trim™ laser trimming for dc precision, paired with an internal guard buffer that actively shields the high-impedance IN+ and IN– traces from PCB leakage. Its input bias current remains ≤20fA (tested max) across –40°C to +85°C at VS = 16V, and ≤75fA at VS = 36V/85°C - enabled by guarded die packaging and low-leakage SOIC pinout design.
It supports single-supply operation from 4.5V to 36V or dual supplies from ±2.25V to ±18V, with rail-to-rail input common-mode range extending to within 0.1V of rails and output swing to within 15mV of rails (no load). The guard buffer operates with 4.5MHz bandwidth, ±8µV offset, and 1kΩ output impedance - directly driving guard traces without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input bias current | 20fA max (tested) at 25°C/85°C, VS = 16V - enables picoampere-level current measurement in photodiode and ion-sensing circuits |
| Input offset voltage | ±5µV - reduces baseline error in high-gain transimpedance amplifiers used in mass spectrometry |
| Offset voltage drift | ±0.1µV/°C - maintains calibration stability over industrial temperature range (–40°C to +125°C) |
| Unity-gain bandwidth | 2.5MHz - supports fast settling (2µs to 0.01%) in high-resolution data acquisition systems |
| Supply range | 4.5V to 36V single or ±2.25V to ±18V dual - accommodates wide-ranging lab equipment power architectures |
| Guard buffer BW | 4.5MHz - ensures synchronous guarding up to mid-frequency signals without phase lag-induced leakage |
| Current noise density | 0.07fA/√Hz at 0.1Hz - minimizes flicker noise contribution in DC-coupled, low-frequency sensor interfaces |
Pinout & Package
OPA928DR is housed in an industry-standard 8-pin SOIC (D package), 4.9mm × 6mm footprint, optimized for low-leakage PCB layouts with guarded trace routing and creepage-enhanced pin spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN+ | Noninverting input | High-impedance node (1000 TΩ || 6 pF) for sensing ultra-low-current sources; requires guard trace |
| IN– | Inverting input | Differential input node; matched to IN+ for common-mode rejection; also guarded |
| V– | Negative supply | Lowest potential rail; must be decoupled locally to minimize noise injection into input stage |
| V+ | Positive supply | Highest potential rail; supports up to +36V; enables wide dynamic range in high-voltage sensor interfaces |
| OUT | Amplifier output | Rail-to-rail capable (≤15mV from rail, no load); drives 2kΩ loads with <500mV drop |
| GRD (Pins 2 & 7) | Guard buffer output | Active shield driven at IN+ common-mode voltage; reduces PCB surface leakage by >40dB |
| DNC (Pin 3) | Do not connect | Internally unused; must remain floating - no trace or pad connection permitted |
Key Features
| Feature | Design Value |
|---|---|
| e-trim™ precision | Laser-trimmed input offset (±5µV) and drift (±0.1µV/°C) - eliminates need for external nulling in production calibration |
| Integrated guard buffer | On-die 4.5MHz buffer with ±8µV offset - replaces discrete op-amp guard drivers and saves board space |
| Rail-to-rail I/O | Input CM range extends to (V–) – 0.1V and (V+) + 0.1V; output swings to within 15mV of rails - maximizes signal headroom in low-voltage systems |
| Femtoampere input bias | 20fA max at 85°C/16V - enables accurate measurement of currents down to 100fA with minimal error contribution |
| Ultra-low current noise | 0.07fA/√Hz at 0.1Hz - preserves signal integrity in DC-coupled, high-source-impedance applications like Coulomb counting |
Applications
| pH Meter Front-End | Mass Spectrometer Detector |
|---|---|
Use Scenario: Amplifying nanoampere-level current from glass electrode in portable and benchtop pH analyzers under varying temperature and humidity. IC Role / Device Role / Timing Role: Transimpedance amplifier with guarded input stage, converting electrode current to stable voltage while rejecting leakage-induced drift. Use Value: 20fA input bias ensures <0.1% error at 10pA input; integrated guard buffer eliminates manual shielding and improves long-term stability. | Use Scenario: Conditioning ion current pulses from electron multiplier detectors in time-of-flight mass spectrometers. IC Role / Device Role / Timing Role: Low-noise, fast-settling amplifier capturing transient ion signals with sub-microsecond rise times and minimal baseline shift. Use Value: 2.5MHz GBW and 2µs 0.01% settling enable accurate peak integration; rail-to-rail output preserves full ADC dynamic range. |
| Ion Chromatography (IC) Conductivity Cell | Lab Electrometer |
Use Scenario: Measuring microsiemens-level conductivity changes across separation columns using AC-excited four-electrode cells. IC Role / Device Role / Timing Role: Precision current-to-voltage converter with guarded inputs, rejecting stray capacitance and cable leakage in high-impedance bridges. Use Value: 1000 TΩ common-mode input impedance and GRD pins suppress humidity-dependent drift; ±5µV offset minimizes zero-point calibration frequency. | Use Scenario: Ultra-high-impedance voltage measurement (<1fA leakage) in semiconductor material characterization and radiation detection setups. IC Role / Device Role / Timing Role: Electrometer-grade amplifier with active guarding, operating in guarded chamber environments with controlled RH <50%. Use Value: Tested 20fA max input bias at 85°C/16V ensures reliable performance in thermal-stressed lab conditions; SOIC pinout supports guarded PCB layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar precision low-input-bias-current amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMP7721MA/NOPB | Higher input bias (3fA typ, 20fA max at 25°C), no integrated guard buffer, 17MHz GBW, 1.9nV/√Hz voltage noise | Better for higher-speed, lower-noise voltage amplification; lacks on-chip guarding for ultra-high-Z layouts | Select when speed >2.5MHz is required and external guarding is feasible |
| ADA4530-1ARZ | Lower input bias (0.1fA typ, 2fA max at 25°C), integrated guard buffer, 2MHz GBW, 10nV/√Hz voltage noise | Superior for femtoampere current measurement; limited bandwidth suits DC/low-frequency electrometers only | Select when ultimate input bias performance is critical and bandwidth ≤2MHz suffices |
Compared with LMP7721MA/NOPB and ADA4530-1ARZ, the OPA928DR uniquely balances 20fA max input bias, 2.5MHz bandwidth, and integrated 4.5MHz guard buffer - making it optimal for high-speed, high-impedance electrochemical sensing where layout simplicity and thermal stability are prioritized.
Availability
OPA928DR is available at Aetrix Electronics and suitable for pH meter manufacturing, mass spectrometer detector modules, and ion chromatography conductivity cell interfaces requiring stable component supply, long-lifecycle support, and guaranteed low-leakage performance.
Supply support for OPA928DR 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 company specializing in analog and embedded processing technologies, with leadership in precision amplifiers, data converters, and power management ICs.
The OPA928DR belongs to TI's e-trim™ precision op-amp product line, engineered specifically for ultra-low-input-bias-current applications in analytical instrumentation, scientific measurement, and high-reliability sensor signal chains.
FAQ
What is the maximum input bias current specification for OPA928DR across temperature?
The OPA928DR has a tested maximum input bias current of 20fA at both 25°C and 85°C with VS = 16V, and 75fA at 85°C with VS = 36V. These values are production-tested per TI SBOSA77A, ensuring guaranteed performance in high-impedance applications like pH meters and electrometers where leakage current directly impacts accuracy. The OPA928DR maintains this spec across its full –40°C to +125°C operating range.
Does OPA928DR require external components for guard buffering?
No, the OPA928DR integrates a high-precision guard buffer with 4.5MHz bandwidth, ±8µV offset, and 1kΩ output impedance - eliminating the need for external op-amps or passive guarding networks. Pins 2 and 7 (GRD) deliver the buffered common-mode voltage directly to PCB guard traces, reducing layout complexity and improving leakage immunity. This on-die feature is confirmed in Section 4 and Table 4-1 of the OPA928DR datasheet.
What supply voltage ranges does OPA928DR support?
The OPA928DR supports single-supply operation from 4.5V to 36V and dual-supply operation from ±2.25V to ±18V. Its rail-to-rail input common-mode range extends to within 0.1V of either supply rail, and output swing reaches within 15mV of rails under no-load conditions. This flexibility allows direct integration into diverse lab equipment architectures - from battery-powered field instruments (4.5V) to high-voltage detector interfaces (36V) - without level-shifting circuitry.
How does the OPA928DR's e-trim™ technology improve system calibration?
The OPA928DR uses TI's e-trim™ laser trimming to achieve ±5µV input offset voltage and ±0.1µV/°C drift - specifications guaranteed over temperature without post-manufacturing adjustment. This eliminates the need for manual potentiometer nulling or digital calibration routines in production, reducing test time and improving long-term stability in deployed systems like ion chromatography analyzers. The OPA928DR's trimmed performance is verified during wafer sort and final test per SBOSA77A.
Can OPA928DR drive capacitive loads, and what is its recommended layout practice?
The OPA928DR can drive capacitive loads up to 100pF stably, as characterized in Figure 5-48 of its datasheet. For higher capacitance, external isolation resistance (e.g., 10–100Ω in series with OUT) is recommended. Layout best practices include: (1) routing IN+, IN–, and GRD traces together with tight coupling; (2) placing GRD traces surrounding sensitive inputs; (3) avoiding solder mask over guard areas; and (4) using the DNC pin (Pin 3) as an unconnected clearance zone - all validated in OPA928DR's layout guidelines (Section 7.4).
OPA928DR 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
OPA928DR FAQ
1.How can I place an order for OPA928DR through Aetrix?
Please submit a Request for Quotation (RFQ) for OPA928DR 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 OPA928DR reliable?
The price and inventory of OPA928DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for OPA928DR is usually 5 days.
3.What payment methods are accepted for OPA928DR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for OPA928DR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for OPA928DR?
OPA928DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your OPA928DR 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 OPA928DR?
For technical support, including OPA928DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your OPA928DR requirements.
6.How does Aetrix verify that OPA928DR is sourced from the original manufacturer or authorized distributors?
All OPA928DR 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 OPA928DR meets industry standards.
7.What is the process for return or replacement of OPA928DR?
All OPA928DR units undergo pre-shipment inspection (PSI). If there is an issue with OPA928DR, 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 OPA928DR part is unused and in its original packaging.
Return procedure for OPA928DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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