1. Products
  2. Amplifiers
  3. Operational Amplifiers (Op Amps)
  4. Low Input Bias Current Op Amps (≤100 pA)
  5. AD8638

Alternative Parts


Features and Benefits

  • Low offset voltage: 9 μV maximum
  • Offset drift: 0.04 μV/°C maximum
  • Rail-to-rail output swing
  • 5 V to 16 V single-supply or ±2.5 V to ±8 V dual-supply operation
  • High gain: 136 dB typical
  • High CMRR: 133 dB typical
  • High PSRR: 143 dB typical
  • Very low input bias current: 40 pA maximum
  • Low supply current: 1.3 mA maximum

Product Details

The AD8638/AD8639 are single and dual wide bandwidth, auto-zero amplifiers featuring rail-to-rail output swing and low noise. These amplifiers have very low offset, drift, and bias current. Operation is fully specified from 5 V to 16 V single supply (±2.5 V to ±8 V dual supply).

The AD8638/AD8639 provide benefits previously found only in expensive zero-drift or chopper-stabilized amplifiers. Using the Analog Devices, Inc., topology, these auto-zero amplifiers combine low cost with high accuracy and low noise. No external capacitors are required. In addition, the AD8638/AD8639 greatly reduce the digital switching noise found in most chopper- stabilized amplifiers.

With a typical offset voltage of only 3 μV, drift of 0.01 μV/°C, and noise of 1.2 μV p-p (0.1 Hz to 10 Hz), the AD8638/AD8639 are suited for applications in which error sources cannot be tolerated. Position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their operating temperature ranges. Many systems can take advantage of the rail-to-rail output swing provided by the AD8638/AD8639 to maximize signal-to-noise ratio (SNR).

The AD8638/AD8639 are specified for the extended industrial temperature range (−40°C to +125°C). The single AD8638 is available in tiny 5-lead SOT-23 and 8-lead SOIC packages. The dual AD8639 is available in 8-lead MSOP, 8-lead SOIC, and 8-lead LFCSP packages.

The AD8638/AD8639 are members of a growing series of auto- zero op amps offered by Analog Devices (see Table 1 in the data sheet).


  • Pressure and position sensors
  • Strain gage amplifiers Medical instrumentation
  • Thermocouple amplifiers Automotive sensors
  • Precision references
  • Precision current sensing
  • Product Lifecycle icon-recommended Production

    At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

    Evaluation Kits (1)

    Documentation & Resources

  • View All (15)
  • Data Sheets (1)
  • Application Notes (1)
  • Technical Books (1)
  • Tutorials (6)
  • Circuit Note (1)
  • Technical Articles (3)
  • Webcasts (2)
  • Tools & Simulations

    SPICE Models

    Design Tools

    Analog Filter Wizard

    Use the Analog Filter Wizard to design low-pass, high-pass, or band-pass filters with actual op amps in minutes. As you progress through the design process, you can observe the characteristics of your filter design from ideal specifications to real world circuit behavior. Quickly evaluate the tradeoffs in op amp specifications - including gain-bandwidth, noise, and supply current – to determine the best filter design for your requirements.

    Analog Photodiode Wizard

    Use Photodiode Wizard to design a transimpedance amplifier circuit to interface with a photodiode. Select a photodiode from the library included in the tool, or enter custom photodiode specifications. Quickly observe tradeoffs between Bandwidth, Peaking (Q), and ENOB/SNR. Modify circuit parameters, and immediately see results in plots for pulse response, frequency response, and noise gain.

    Reference Designs (1)

    Design Resources

    ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.

    Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
    AD8638ARJZ-REEL7 Material Declaration Reliability Data 5-Lead SOT-23
    AD8638ARZ Material Declaration Reliability Data 8-Lead SOIC
    AD8638ARZ-REEL Material Declaration Reliability Data 8-Lead SOIC
    AD8638ARZ-REEL7 Material Declaration Reliability Data 8-Lead SOIC
    Wafer Fabrication Data

    PCN-PDN Information

    Select a model from the dropdown below to subscribe to PCN/PDN notifications and view past notifications as well.

    Sample & Buy

    Ordering FAQs

    See our Ordering FAQs for answers to questions about online orders, payment options and more.


    Buy Now Pricing

    (**) Displayed Buy Now Price and Price Range is based on small quantity orders.


    List Pricing

    (*)The 1Ku list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


    Lead Times

    Please see the latest communication from our CCO regarding lead times.



    Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.

    Price Table Help


    Evaluation Boards

    Pricing displayed is based on 1-piece.

    Up to two boards can be purchased through Analog.com. To order more than two, please purchase through one of our listed distributors.

    Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.