Analog Devices Inc./Maxim Integrated ICL7611BCSA+

Overview

ICL7611BCSA+ from Maxim Integrated is a single-channel, ultra-low-input-bias-current CMOS operational amplifier with pin-selectable quiescent current (10 μA / 100 μA / 1 mA), ±1 V to ±8 V dual-supply operation (or 2–16 V single supply), 1 pA typical input bias current at +25°C, and rail-to-rail output swing within millivolts of supply rails. It serves as a precision front-end amplifier in high-impedance sensor interfaces such as pH meters and photodiode amplifiers.

For engineers reviewing the ICL7611BCSA+ datasheet, ICL7611BCSA+ pinout, ICL7611BCSA+ application, or ICL7611BCSA+ equivalent, key selection criteria include confirmed 1 pA bias current performance at 0°C to +70°C, programmable IQ configuration, offset null capability, and compatibility with low-leakage integrator and picoammeter topologies requiring sub-picoampere input errors.

Technical Context

The ICL7611BCSA+ implements a monolithic CMOS input stage enabling 10¹² Ω input impedance and 0.01 pA/√Hz input noise current - critical for guarding against leakage-induced error in high-Z source applications. Its quiescent current is set via external voltage applied to the IOSET pin, directly scaling unity-gain bandwidth (0.044 MHz at 10 μA → 1.4 MHz at 1 mA) and slew rate (0.016 V/μs → 1.6 V/μs) without altering output sourcing capability.

Unlike fixed-IQ dual/quad variants, the ICL7611BCSA+ supports full offset nulling via external 25 kΩ potentiometer across OFFSET pins, with null range sufficient for its B-grade 5 mV max V_OS at 100 μA and 1 mA IQ settings. Internal compensation ensures stable unity-gain operation; no external capacitor required unless using ICL7614 variant.

Key Specifications

Pinout & Package

ICL7611BCSA+ is housed in an 8-pin Small Outline (SO) package (SA code), surface-mount compatible with JEDEC MS-012AC footprint, 3.9 mm × 4.9 mm body, 1.75 mm height, and 1.27 mm lead pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-bias-current op amp applications.

Compared with LTC1050CS8#PBF and TLC27L1CDR, the ICL7611BCSA+ uniquely balances guaranteed 1 pA bias current across 0°C to +70°C, user-adjustable IQ for power/bandwidth tuning, and dedicated offset null terminals - making it the preferred choice for production pH meters and calibrated picoammeters requiring traceable calibration.

Availability

ICL7611BCSA+ is available at Aetrix Electronics and suitable for pH meter front-ends, photodiode transimpedance amplifiers, and low-droop sample/hold circuits requiring stable component supply across multi-year production cycles.

Supply support for ICL7611BCSA+ 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 industrial, medical, and communications applications.

The ICL761X family was engineered specifically for ultra-high-impedance, low-power signal conditioning - targeting electrochemical sensors, radiation detectors, and portable instrumentation where femtoampere-level leakage must be controlled.

FAQ

What is the guaranteed maximum input bias current for ICL7611BCSA+ over its full operating temperature range?

The ICL7611BCSA+ guarantees a maximum input bias current of 500 pA across its specified 0°C to +70°C operating temperature range. At +25°C, typical performance is 1 pA, and the datasheet confirms ≤500 pA under worst-case C-temp conditions - critical for validating long-term integrator accuracy and picoammeter resolution in production designs using ICL7611BCSA+.

Does ICL7611BCSA+ require external frequency compensation?

No, the ICL7611BCSA+ is internally compensated for stable unity-gain operation. Unlike the ICL7614 variant, it does not require an external capacitor between COMP and OUT pins. This simplifies PCB layout and eliminates compensation tuning - a key reliability advantage for ICL7611BCSA+ in volume-manufactured pH meters and portable analyzers.

How is quiescent current configured on ICL7611BCSA+?

Quiescent current on ICL7611BCSA+ is set by applying a voltage to the IOSET pin (Pin 7): connect to V+ for 10 μA, to a mid-rail voltage (V– + 0.8 V to V+ – 0.8 V) for 100 μA, or to V– for 1 mA. This direct voltage control allows real-time power/performance adaptation - a feature not found in fixed-IQ alternatives like TLC27L1CDR, and central to ICL7611BCSA+'s flexibility in battery-constrained designs.

Can ICL7611BCSA+ operate from a single 3.3V supply?

Yes, ICL7611BCSA+ supports single-supply operation from 2 V to 16 V. At 3.3 V, it delivers rail-to-rail output swing (typically ±1.6 V), maintains 1 pA input bias current, and achieves usable bandwidth (e.g., ~0.04 MHz at 10 μA IQ). This makes ICL7611BCSA+ suitable for modern low-voltage IoT sensor nodes and wearable medical devices where 3.3 V logic rails are standard.

What is the purpose of the two OFFSET pins on ICL7611BCSA+?

The two OFFSET pins (Pins 5 and 6) on ICL7611BCSA+ provide dedicated connections for an external 25 kΩ potentiometer to null input offset voltage. The wiper connects to V+, enabling precise trimming of V_OS - especially valuable for DC-coupled applications like pH meter front-ends where untrimmed 5 mV V_OS would introduce significant measurement error. This hardware-level trimming capability is absent in many competing low-power op amps and is integral to ICL7611BCSA+'s role in calibrated instrumentation.