STMicroelectronics OA4ZHA33Q

Overview

OA4ZHA33Q from STMicroelectronics is a quad-channel, chopper-stabilized, rail-to-rail input/output operational amplifier optimized for ultra-precision analog signal conditioning in low-power wearable and medical instrumentation. It delivers 5 µV max input offset voltage at 25 °C, 8 µV over –40 °C to 125 °C, 400 kHz gain bandwidth, and 40 µA max supply current per amplifier at 5 V - enabling high-accuracy DC-coupled sensing without calibration.

For engineers reviewing the OA4ZHA33Q datasheet, OA4ZHA33Q pinout, OA4ZHA33Q application, or OA4ZHA33Q equivalent, key selection criteria include zero-drift performance across temperature, EMI robustness (84–91 dB EMIRR at 400–2400 MHz), rail-to-rail operation down to 1.8 V, and QFN16 3×3 package suitability for space-constrained healthcare PCBs.

Technical Context

The OA4ZHA33Q employs a dual-chopper architecture with 400 kHz internal clock modulation and synchronous demodulation to cancel input offset voltage and 1/f noise in real time. Its CMOS input stage achieves ultra-low input bias current (70–300 pA) and high common-mode rejection (115–136 dB) across 1.8–5.5 V supply range.

It features integrated ESD protection (4 kV HBM), rail-to-rail output swing within 30 mV of rails (at 10 kΩ load), and stable operation with capacitive loads up to 100 pF - validated via phase margin ≥53° and gain margin ≥17 dB across all supply voltages.

Key Specifications

Pinout & Package

OA4ZHA33Q is packaged in a wettable flank QFN16 3×3 mm, 0.5 mm pitch package with exposed thermal pad (connected to VCC– or left floating). Pin 1 marked by dot; top-side marking "OA4ZHA33Q".

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision chopper op amp applications.

Compared with AD8628ARZ-REEL7 and MAX44265ASA+, OA4ZHA33Q uniquely combines quad integration, QFN16 footprint, 91 dB 2.4 GHz EMIRR, and <40 µA/channel consumption - making it the only drop-in solution for miniaturized, multi-parameter, wireless-connected medical sensors requiring zero-drift stability across temperature and RF environments.

Availability

OA4ZHA33Q is available at Aetrix Electronics and suitable for wearable health monitors, portable ECG patches, and disposable biosensor modules requiring stable component supply across extended temperature and long-lifecycle production programs.

Supply support for OA4ZHA33Q 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, analog ICs, power management, and MEMS sensors for industrial, automotive, and consumer markets.

The OA4ZHA series belongs to ST's high-precision analog portfolio, engineered specifically for battery-powered medical and fitness devices where zero-drift performance, ultra-low power, and RF resilience are non-negotiable design requirements.

FAQ

What is the maximum capacitive load the OA4ZHA33Q can drive stably?

OA4ZHA33Q maintains stability with capacitive loads up to 100 pF when driving a 10 kΩ resistive load, as verified by phase margin ≥53° and absence of peaking in Bode plots. For loads >100 pF, an external series resistor (≥10 Ω) between output and capacitance is required to preserve 55° minimum phase margin per datasheet Figure 29.

Does the exposed thermal pad on the QFN16 package require electrical connection?

Per datasheet Section 1, the exposed pad may be connected to VCC– (GND) for optimal thermal performance and EMI shielding, or left electrically floating. ST recommends soldering the pad to a dedicated thermal land tied to VCC– plane; no voltage or current rating applies - it serves only thermal and mechanical functions.

Can OA4ZHA33Q operate with asymmetric supplies, e.g., VCC+ = 3.3 V and VCC– = –1.8 V?

No. OA4ZHA33Q is specified only for single-supply operation from 1.8 V to 5.5 V referenced to VCC– (GND). The absolute maximum rating for differential supply is 6 V, and common-mode input range is defined relative to VCC–; negative supply configurations violate operating conditions in Table 2 and risk latch-up or parametric failure.

How does the chopper clock frequency affect system-level noise performance?

The internal 400 kHz chopper clock generates residual ripple at harmonics (400 kHz, 800 kHz, etc.), suppressed to <1 µVpp by on-chip low-pass filtering. At baseband (<10 Hz), input-referred noise is 37 nV/√Hz (typ.) - effectively eliminating 1/f noise. External RC filtering beyond 10 kHz further attenuates switching artifacts in sensitive bio-potential measurements.