Analog Devices Inc./Maxim Integrated MAX4128EUA

Overview

MAX4128EUA from Maxim Integrated is a dual, decompensated, rail-to-rail input/output operational amplifier optimized for high-speed, low-power, single-supply signal conditioning. It delivers 25MHz gain-bandwidth product, 10V/µs slew rate, and 650µA quiescent current per amplifier while operating from +2.7V to +6.5V. It drives 250Ω loads and supports stable operation at closed-loop gains ≥10 - ideal for precision data-acquisition front-ends in portable instrumentation.

For engineers reviewing the MAX4128EUA datasheet, MAX4128EUA pinout, MAX4128EUA application, or MAX4128EUA equivalent, key selection criteria include its decompensated stability requirement (G ≥10), rail-to-rail I/O swing down to 1.8V operation, 200µV max input offset voltage, capacitive-load tolerance up to 500pF, and µMAX-8 package compatibility with space-constrained PCB layouts.

Technical Context

The MAX4128EUA implements a composite NPN/PNP rail-to-rail input stage enabling common-mode range extension 250mV beyond VEE and VCC, with switchover near VCC/2 to minimize CMRR degradation. Its decompensated architecture achieves 25MHz GBW by sacrificing unity-gain stability - requiring minimum closed-loop gain of 10V/V for phase margin >60°.

It features matched dual amplifiers sharing one shutdown control (SHDN) pin that places both outputs in high-impedance state and reduces supply current to ≤70µA total when asserted. Output stage delivers rail-to-rail swing into 250Ω loads with <150mV headroom at VCC = 6.5V and maintains stability with 500pF capacitive loads without external compensation.

Key Specifications

Pinout & Package

MAX4128EUA is housed in an 8-pin µMAX package (pin-compatible with SO-8), measuring 3mm × 3mm × 0.8mm with exposed pad for thermal enhancement. The package supports reflow soldering and provides low-inductance connections for high-frequency performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual, high-speed, rail-to-rail op amp applications.

Compared with MAX4126EUA and AD8602ARZ, the MAX4128EUA uniquely combines decompensated 25MHz bandwidth, rail-to-rail I/O, and integrated shutdown in µMAX-8 - making it optimal for G ≥10, battery-sensitive, high-fidelity signal chains where speed and power efficiency are jointly constrained.

Availability

MAX4128EUA is available at Aetrix Electronics and suitable for battery-powered instrumentation, industrial data-acquisition systems, and portable medical sensors requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for MAX4128EUA 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) designs precision analog, mixed-signal, and power-management ICs for demanding industrial, automotive, and communications applications.

The MAX4122–MAX4129 family was engineered specifically for low-voltage, rail-to-rail signal conditioning in portable and precision measurement systems - balancing speed, power, accuracy, and ease of use in single-supply environments.

FAQ

What is the minimum closed-loop gain required for stable operation of the MAX4128EUA?

The MAX4128EUA is decompensated and requires a minimum closed-loop gain of 10V/V (G ≥ 10) to ensure phase margin >60° and prevent oscillation. This is explicitly specified in the datasheet's AC Electrical Characteristics table and confirmed in Gain vs. Frequency plots. Operating the MAX4128EUA at G = 1 will result in instability and is not supported. Designers must verify gain-setting resistor ratios meet this constraint in all MAX4128EUA applications.

Does the MAX4128EUA support true rail-to-rail input common-mode voltage range?

Yes, the MAX4128EUA supports a rail-to-rail input common-mode voltage range extending 250mV beyond both supply rails (VEE – 0.25V to VCC + 0.25V) at room temperature, and VEE – 0.2V to VCC + 0.2V over –40°C to +85°C. This is achieved via complementary NPN/PNP input pairs, enabling direct interfacing with sensors whose outputs swing near ground or VCC - a key advantage over conventional op amps in single-supply systems.

Can the MAX4128EUA drive a 500pF capacitive load without external compensation?

Yes, the MAX4128EUA is explicitly characterized and guaranteed stable with capacitive loads up to 500pF, as stated in the "Capacitive Load Stability" parameter (500pF) and verified in Figure 4 (Capacitive-Load Stability) and Figures 5–6 (transient response). No series isolation resistor or feedback capacitor is required for stability at this load - simplifying layout and preserving bandwidth in ADC driver and filter applications.

What happens to the outputs of the MAX4128EUA during shutdown mode?

When the SHDN pin is pulled low (<0.8V), both amplifier outputs (OUT1 and OUT2) enter a high-impedance (Hi-Z) state, effectively disconnecting them from the load. Simultaneously, total supply current drops to ≤70µA. This behavior is confirmed in the DC Electrical Characteristics table ("Off-Leakage Current") and Figures 13–14 (shutdown output voltage and current waveforms). The Hi-Z state prevents loading of downstream circuitry during sleep modes.

Is the MAX4128EUA pin-compatible with other devices in the MAX412x family?

The MAX4128EUA uses the µMAX-8 package and shares identical pinout with MAX4126EUA, MAX4123EUA, and MAX4125EUA - all featuring OUT1, IN1–, IN1+, VEE, VCC, IN2+, IN2–, and SHDN on pins 1–8 respectively. However, internal compensation differs: MAX4128EUA is decompensated (G ≥10), while MAX4126EUA is unity-gain stable. Swapping them requires verifying gain configuration to avoid instability.