STMicroelectronics LM324QT

Overview

LM324QT from STMicroelectronics is a quad low-power operational amplifier in QFN16 3x3 package, designed for single-supply operation from 3 V to 30 V. It delivers 1.3 MHz gain bandwidth, 100 dB large-signal voltage gain, and rail-to-rail input common-mode range including ground-enabling precision signal conditioning in industrial sensor interfaces and battery-powered instrumentation.

For engineers reviewing the LM324QT datasheet, LM324QT pinout, LM324QT application, or LM324QT equivalent, key selection criteria include its 375 µA/amplifier supply current, 3 mV max input offset voltage (LM324A-grade), 20 nA input bias current, and guaranteed operation across 0 °C to 70 °C ambient temperature.

Technical Context

The LM324QT implements internally frequency-compensated, high-gain DC-coupled amplifiers with PNP input stage enabling ground-sensing capability. Its architecture supports stable unity-gain operation and tolerates input voltages down to –0.3 V relative to VCC–, while maintaining 120 dB channel separation up to 20 kHz.

It features rail-to-rail output swing (within ~1.5 V of rails at full load), 40 mA short-circuit protected output drive, and thermal shutdown protection. The QFN16 3x3 package includes an exposed thermal pad that may be connected to VCC– for improved thermal resistance (R_thJA = 45 °C/W).

Key Specifications

Pinout & Package

LM324QT is housed in a 3 mm × 3 mm QFN16 package with wettable flank leads and an exposed thermal pad on the underside. The pad is electrically connected to VCC– and must be soldered to a PCB thermal plane for optimal thermal performance (R_thJC = 14 °C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad op-amp applications.

Compared with LM324PT, LM324QT offers 2.2× better thermal performance and smaller footprint; versus TSB572IDT, it trades higher precision and voltage range for 4.8× lower quiescent current and broader legacy compatibility.

Availability

LM324QT is available at Aetrix Electronics and suitable for industrial sensor interfaces, portable medical devices, smart energy metering, and automotive cabin electronics requiring stable component supply across long production lifecycles.

Supply support for LM324QT 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, Switzerland, specializing in automotive, industrial, and power management ICs with strong analog portfolio heritage.

The LM324x series belongs to ST's general-purpose operational amplifier product line, engineered for cost-sensitive, high-volume applications demanding reliability, wide supply range, and ease of use in single-supply systems.

FAQ

What is the maximum junction temperature for LM324QT?

The absolute maximum junction temperature is 150 °C. With R_thJA = 45 °C/W and 1.5 mA total supply current (at V_CC = 30 V), power dissipation is ~45 mW; under natural convection on a 2-layer board with thermal pad connected, junction rise is ~2 °C - well within safe margin for continuous operation at 70 °C ambient.

Can LM324QT drive a 10 kΩ load to rail in single-supply mode?

Yes. At V_CC = 30 V and room temperature, high-level output voltage is 27 V min into 10 kΩ (≥90% of rail), and low-level output is ≤20 mV. Output swing degrades slightly at temperature extremes but remains functional across the full 0 °C to 70 °C range per datasheet Table 3.

Is the exposed thermal pad on LM324QT electrically connected?

Yes - the exposed pad is internally connected to VCC– (pin 4). It must be soldered to a PCB copper pour tied to the same net to achieve rated R_thJA = 45 °C/W. Leaving it floating increases thermal resistance by >3× and risks thermal runaway under sustained load.

How does LM324QT differ from LM324DT in SO14 package?

LM324QT (QFN16) and LM324DT (SO14) share identical electrical specifications and temperature grade (0 °C to 70 °C), but differ mechanically: QFN16 offers 60% smaller footprint, 3× better thermal performance, and wettable flanks for automated optical inspection; SO14 provides through-hole compatibility and easier prototyping with breadboards.