LM2901DR2G Quad Differential Comparator: Datasheet, Pinout, and Application Circuits

The LM2901DR2G is a widely used, industry-standard quad independent voltage comparator. Housed in a compact SOIC-14 package, this device is designed to operate from a single power supply over a wide range of voltages, making it an extremely versatile component for a multitude of analog circuit designs. Its key attributes include low power consumption, wide supply voltage range, and compatibility with both TTL and CMOS logic outputs.

Datasheet Overview and Key Specifications

A thorough review of the LM2901DR2G datasheet reveals its robust electrical characteristics. The device features low supply current,

independent of the supply voltage, making it ideal for battery-powered applications. Its wide single-supply voltage range of 2V to 36V (or ±1V to ±18V for dual supplies) provides exceptional flexibility. The device exhibits a low input bias current and a low input offset voltage, ensuring accurate comparison even with small differential signals. Furthermore, the open-collector outputs allow for easy interfacing with other logic families by simply connecting an external pull-up resistor to the desired logic voltage rail (e.g., 5V or 3.3V).

Pinout Configuration

The LM2901DR2G in the SOIC-14 package has a standardized pin configuration:

Pins 1, 7, 8, 14: Outputs of the four comparators (Output 1, 2, 3, 4).

Pins 2, 4, 5, 6: Inverting Inputs (-Input) for the four comparators.

Pins 3, 4, 5, 6: Non-Inverting Inputs (+Input) for the four comparators. (Note: Pins 4, 5, 6, 7 are shared for different functions for different comparators; careful attention is needed).

Pin 8: Ground (GND).

Pin 14: Positive Supply Voltage (VCC+).

Classic Application Circuits

1. Basic Voltage Comparator: The most fundamental circuit. The non-inverting input is connected to a reference voltage, while the inverting input is fed with a sensing voltage. The output switches from low to high (if using a pull-up resistor) when the sensing voltage drops below the reference.

2. Window Comparator: This circuit uses two of the device's four comparators to determine if an input voltage lies within a specific "window" defined by two reference voltages (a high and a low limit). The output is active only when the input is between these two thresholds.

3. Simple Analog-to-Digital (A/D) Converter: By using a resistive ladder network to create multiple reference voltages for each comparator's inverting input, the LM2901 can function as a flash A/D converter. The parallel outputs provide a fast, thermometric code representing the input voltage level.

4. Oscillator / Square Wave Generator: By configuring a comparator with positive feedback (hysteresis), also known as a Schmitt trigger, the LM2901 can be used to create a simple relaxation oscillator. This circuit generates a continuous square wave, whose frequency is determined by an RC time constant.

ICGOODFIND: The LM2901DR2G stands as a fundamental building block in electronic design. Its quad package offers high density, its wide supply range ensures design flexibility, and its simple output interface simplifies system integration. For tasks involving level detection, sensing, waveform generation, or analog-to-digital conversion, this comparator remains a top choice for engineers seeking reliable and cost-effective performance.

Keywords: Voltage Comparator, Open-Collector, Wide Supply Voltage, Quad Differential, SOIC-14