ADI AD549

AD549 General Description

The AD549 is a highly precise monolithic electrometer operational amplifier designed with an emphasis on low input bias current. It features laser-trimmed input offset voltage and offset voltage drift to ensure precision performance. The ultralow input current is achieved through Topgate™ JFET technology, exclusive to Analog Devices, which allows for the creation of extremely low input current JFETs while maintaining compatibility with a standard junction-isolated bipolar process.

The AD549 boasts a 10^15 Ω common-mode impedance, thanks to its bootstrapped input stage, ensuring that input current remains essentially independent of common-mode voltage. This makes it suitable for applications requiring very low input current and low input offset voltage.

AD549 Manufacturer

The AD549 is an operational amplifier (op-amp) manufactured by Analog Devices, Inc. Analog Devices is a well-known semiconductor company that produces a wide range of integrated circuits and analog and digital signal processing products. The AD549 is part of Analog Devices' portfolio of precision operational amplifiers and is designed for applications requiring high precision and low noise in amplification and signal conditioning circuits.

Analog Devices, Inc. (ADI) is a publicly traded corporation renowned for its expertise in designing, developing, and manufacturing cutting-edge analog, mixed-signal, and digital signal processing (DSP) integrated circuits (ICs). Established back in 1965, the company has its headquarters nestled in Norwood, Massachusetts.

AD549 Specification

Features

• Low Input Bias Current: The AD549 is designed with very low input bias currents, which is crucial for applications where input current must be minimized to prevent errors, especially in high-impedance circuits.
• Laser-Trimmed Input Offset Voltage: Its input offset voltage is laser-trimmed for precision performance. This ensures that the amplifier's output voltage is as close to zero as possible when the inputs are shorted.
• Low Input Offset Voltage Drift: The AD549 has low input offset voltage drift over temperature, which helps maintain accuracy in varying operating conditions. The AD549K version offers even lower drift than the AD549J.
• Low Quiescent Supply Current: With a maximum quiescent supply current of 700 μA, the AD549 minimizes power consumption, reducing the impact of heating effects on input current and offset voltage.
• Wide Common-Mode Input Voltage Range: The AD549 supports a wide common-mode input voltage range, making it versatile for various input signal levels.
• High Unity-Gain Bandwidth: It has a high unity-gain bandwidth of 1 MHz, making it suitable for high-frequency applications.
• Fast Slew Rate: The AD549 offers a 3 V/μs slew rate, allowing it to quickly respond to changes in input signals.
• Fast Settling Time: It has a fast settling time of 5 μs to reach 0.01% for a 10 V input step, ensuring rapid settling in dynamic applications.
• Pin-Compatible: The AD549 is pin-compatible with standard FET and electrometer op-amps, making it easy to upgrade existing systems for improved performance without significant redesign.
• Hermetic Package: It is available in a TO-99 hermetic package, with the case connected to Pin 8. This allows for independent connection to a point at the same potential as the input terminals, minimizing stray leakage to the case.
• Temperature Grades: The AD549 is available in different temperature grades, including commercial (0°C to +70°C) and military (-55°C to +125°C), meeting various application requirements.

AD549 Related Parts

AD549 Highlights

• Guaranteed Input Currents: The AD549 specifies, 100% tests, and guarantees input currents after device warm-up. These specifications are guaranteed across the entire common-mode input voltage range.
• Precisely Trimmed Offset: The input offset voltage and drift of the AD549 are laser trimmed to 0.50 mV and 15 μV/°C for the AD549K version, and 1 mV and 20 μV/°C for the AD549J version, ensuring high precision.
• Low Quiescent Supply Current: It has a maximum quiescent supply current of 700 μA, minimizing heat effects on input current and offset voltage.
• AC Performance: The AD549 offers excellent AC performance with a 1 MHz unity-gain bandwidth and a 3 V/μs slew rate. The settling time for a 10 V input step is 5 μs to reach 0.01%.

Application

• Photodiode Amplifiers: The AD549 is often used as a preamp for photodiodes, which are light-sensitive devices. Its low input bias current and offset voltage make it suitable for amplifying small photocurrents accurately.
• Photomultiplier Tube (PMT) Amplifiers: PMTs are highly sensitive detectors used in applications such as spectroscopy and radiation detection. The AD549 can amplify the tiny currents generated by PMTs with high precision.
• Oxygen Sensors: Oxygen sensors often produce small current signals that need amplification. The AD549's low input bias current and low offset voltage are beneficial in such applications.
• Precision Instrumentation: The AD549 is ideal for precision measurement and instrumentation applications, where low noise, low drift, and high accuracy are essential. It can be used in data acquisition systems, temperature measurement, and more.
• Active Filters: The AD549 can be used in active filter designs, such as low-pass, high-pass, or band-pass filters, to process and filter analog signals with precision.
• Voltage and Current Sources: It can serve as a high-precision voltage or current source in various circuits, ensuring stable and accurate outputs.
• Precision Integrators: The AD549 can be used to implement precision integrators in applications like signal processing and control systems.
• Sample-and-Hold Circuits: Due to its fast settling time and low offset voltage, the AD549 can be employed in sample-and-hold circuits that require minimal droop and high precision.
• Signal Conditioning: In general, the AD549 can be used for signal conditioning tasks where maintaining signal accuracy and minimizing errors are crucial.
• Upgrade Existing Systems: The AD549 is pin-compatible with standard FET and electrometer op-amps, making it a straightforward choice to upgrade the performance of existing systems without significant hardware modifications.

AD549 Absolute Maximum Ratings

AD549 Equivalent Parts

• Analog Devices AD548: This is another precision operational amplifier from Analog Devices that shares some characteristics with the AD549, such as low input bias current and offset voltage.
• Texas Instruments OPA227: TI offers a range of precision operational amplifiers, and the OPA227 is known for its low input bias current and low offset voltage.
• Linear Technology (now part of Analog Devices) LT1007: The LT1007 is a precision operational amplifier known for its low input bias current and low offset voltage. It's available through Analog Devices.
• STMicroelectronics TSZ182: STMicroelectronics offers precision operational amplifiers, and the TSZ182 is an example with low input bias current and low offset voltage.
• Maxim Integrated MAX4239: Maxim Integrated produces precision operational amplifiers with similar characteristics to the AD549, such as low input bias current and low offset voltage.

Specifications