LM2901VDG Quad Differential Comparator: Datasheet, Application Circuit, and Pinout Configuration
The LM2901VDG is a member of a renowned family of quad differential comparators, designed to operate from a single power supply over a wide voltage range. This device integrates four independent, high-gain voltage comparators in a single package, making it an exceptionally cost-effective and space-saving solution for a multitude of analog signal processing tasks. Its robust design and wide operating voltage make it suitable for industrial, automotive, and consumer applications.
Pinout Configuration
The LM2901VDG is commonly available in a SOIC-14 package. The pinout is standardized for quad comparators:
Pins 1, 7, 8, 14 (Outputs 1-4): These are the open-collector outputs for each comparator. They require an external pull-up resistor to the desired logic high voltage level.
Pins 2, 4, 5, 9 (Inverting Inputs 1-4): The inverting (-) inputs for the four comparators.
Pins 3, 6, 10, 11 (Non-Inverting Inputs 1-4): The non-inverting (+) inputs for the four comparators.
Pin 12 (GND): Ground pin.
Pin 13 (VCC+): Positive power supply pin.
Key Datasheet Specifications
Understanding the critical parameters from the datasheet is essential for proper design:
Wide Supply Voltage Range: Can operate from 3V to 36V with a single supply, or from ±1.5V to ±18V with a dual supply.
Low Supply Current: Typically draws only 0.8 mA per comparator, independent of the supply voltage, which is ideal for battery-powered systems.
Low Input Bias Current: Typically 25 nA, minimizing the error introduced by the comparator's input circuitry.
Common-Mode Input Voltage Range: Includes ground (0V), allowing it to sense signals near the negative rail.
Differential Input Voltage Range: Equal to the supply voltage, providing design flexibility.
Output Saturation Voltage: Low output voltage when active, compatible with driving TTL, CMOS, and other logic families.
Application Circuit: Basic Light Level Sensor
A classic application for the LM2901VDG is a light-sensing circuit. One of its four comparators can be easily configured for this task.
Components Required:
LM2901VDG (one comparator used)
Photoresistor (LDR)
Fixed resistor (e.g., 10kΩ potentiometer for adjustable threshold)
Pull-up resistor (e.g., 10kΩ)
LED (with current-limiting resistor)
Circuit Operation:
1. A voltage divider is created using the photoresistor and a fixed resistor. The node between them is connected to the non-inverting input (+)
2. A second voltage divider, made from two fixed resistors, creates a stable reference voltage. This is connected to the inverting input (-).
3. The open-collector output is connected to VCC through a pull-up resistor and an LED.
4. When the light level is high, the resistance of the photoresistor is low. This causes the voltage at the non-inverting input to fall below the reference voltage at the inverting input.
5. The comparator output turns on, sinking current to ground and illuminating the LED.
6. When the light level drops, the photoresistor's resistance increases, raising the voltage at the non-inverting input above the reference. This causes the comparator output to turn off (go high impedance), and the LED turns off.
This simple circuit demonstrates the fundamental principle of comparing an analog sensor signal to a fixed threshold to create a digital on/off output.
ICGOODFIND Summary
The LM2901VDG stands out as an industry-standard, highly versatile quad comparator. Its wide operating voltage range, low power consumption, and ability to interface directly with logic systems make it an indispensable component for designers. From simple threshold detection and oscillator circuits to complex window comparators and level translators, the LM2901VDG provides reliable performance and four channels of functionality in a single, economical IC, solidifying its status as a fundamental building block in electronic design.
Keywords: Quad Comparator, Wide Supply Voltage, Open-Collector Output, Differential Input, Threshold Detection.
