Analog Devices Inc./Maxim Integrated MAX9945ATT+T

Overview

MAX9945ATT+T from Maxim Integrated is a 38V, low-noise, MOS-input operational amplifier optimized for high-impedance sensor front-ends, delivering 15nV/√Hz input voltage noise, 1fA/√Hz input current noise, and rail-to-rail output swing with only 400µA quiescent current. It operates from ±2.4V to ±19V dual supply or +4.75V to +38V single supply and is specified over –40°C to +125°C for automotive-grade reliability in photodiode transimpedance and chemical sensor interface circuits.

For engineers reviewing the MAX9945ATT+T datasheet, MAX9945ATT+T pinout, MAX9945ATT+T application, or MAX9945ATT+T equivalent, key selection criteria include its 50fA typical input bias current, 3MHz unity-gain bandwidth, 130dB open-loop gain, and validated stability with 120pF capacitive loads-critical for precision analog signal conditioning in portable medical and industrial systems.

Technical Context

The MAX9945ATT+T employs a BiCMOS process with MOS input transistors to achieve ultra-low input bias current (50fA typ) and sub-1fA/√Hz input current noise, enabling accurate amplification of picoamp-level photodiode or electrochemical sensor currents. Its input common-mode range extends from VEE to VCC – 1.2V, supporting wide-supply operation without level-shifting.

Rail-to-rail output stage delivers <50mV saturation voltage at both rails under 100kΩ load, while maintaining 2.2V/µs slew rate and unity-gain stability-enabling clean, distortion-free signal buffering and active filtering up to 10kHz with THD of –97dB at 10kHz.

Key Specifications

Pinout & Package

MAX9945ATT+T is housed in a 6-pin TDFN-EP package (3mm × 3mm, exposed pad), optimized for thermal performance and space-constrained PCB layouts in portable medical and automotive modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, high-impedance op amp applications.

Compared with ADA4530-1ARZ and LTC6268IMS8#PBF, the MAX9945ATT+T uniquely balances ultra-low input bias current (50fA), low power (400µA), rail-to-rail output, and 3MHz bandwidth in a 6-pin TDFN-making it optimal for space- and power-constrained portable medical and industrial sensor nodes where both current and voltage noise matter.

Availability

MAX9945ATT+T is available at Aetrix Electronics and suitable for portable medical devices, automotive cabin air quality monitors, and industrial chemical analyzers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX9945ATT+T 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

Maxim Integrated (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, medical, and automotive markets.

The MAX9945ATT+T belongs to Maxim's precision low-noise op amp product line, designed specifically for high-impedance sensor signal chains in battery-operated and thermally demanding environments.

FAQ

What is the maximum capacitive load the MAX9945ATT+T can drive without oscillation?

The MAX9945ATT+T is specified to remain stable with up to 120pF capacitive load across the full –40°C to +125°C temperature range, as confirmed by circuit simulation and production testing. This capability eliminates the need for external isolation resistors when driving ADC input capacitance or long PCB traces, simplifying layout in compact sensor modules where the MAX9945ATT+T serves as the first-stage amplifier.

Does the MAX9945ATT+T support single-supply operation, and what is the minimum supply voltage?

Yes, the MAX9945ATT+T supports true single-supply operation from +4.75V to +38V, with rail-to-rail output swing down to within 50mV of VEE (ground in single-supply mode). The 4.75V minimum enables compatibility with standard 5V logic rails and regulated 5V supplies, while its ability to operate up to +38V allows direct connection to unregulated 24V industrial buses-making the MAX9945ATT+T suitable for both portable and ruggedized applications.

How does the input bias current of the MAX9945ATT+T affect transimpedance amplifier accuracy?

The MAX9945ATT+T's typical input bias current of 50fA introduces negligible offset error in transimpedance amplifiers using feedback resistors ≤1GΩ, and remains below 1pA even at +125°C. This ensures stable DC operating points and minimal drift in photodiode pulse oximetry circuits where dark current calibration is critical-directly enhancing long-term measurement repeatability of the MAX9945ATT+T in clinical-grade devices.

Is the exposed pad (EP) on the MAX9945ATT+T package electrically connected?

No, the exposed pad (EP) on the MAX9945ATT+T's 6-pin TDFN package is not an electrical terminal-it is a thermal pad that must be soldered to a large copper plane connected to VEE for optimal heat dissipation. Electrical connection to VEE via the EP is recommended to improve thermal resistance (θ_JA = 42°C/W), but the pad itself carries no signal or power function beyond thermal management in the MAX9945ATT+T design.

What is the guaranteed open-loop gain of the MAX9945ATT+T over temperature?

The MAX9945ATT+T guarantees a minimum open-loop gain (A_OL) of 110dB across the full –40°C to +125°C operating range, with typical performance at 130dB at +25°C. This high, stable gain ensures <0.1% closed-loop gain error in precision instrumentation amplifier configurations using moderate gains (e.g., 100V/V), directly contributing to measurement accuracy in chemical sensor interface circuits using the MAX9945ATT+T.