LM311N Voltage Comparator

Overview

The LM311N is a high-performance voltage comparator belonging to the LM111/LM211/LM311 family. It is designed to offer significantly lower input currents compared to older comparator models such as the LM106 or LM710. This device is highly versatile, capable of operating across a wide range of supply voltages, from standard ±15V op-amp supplies down to a single 5V logic supply. The LM311N is particularly well-suited for applications requiring compatibility with various logic families, including RTL, DTL, TTL, and MOS circuits. Additionally, it can drive high-voltage loads such as lamps or relays, with switching capabilities up to 50V and 50mA.

Features

• Low Input Current: Input currents are nearly a thousand times lower than older comparator models, enhancing precision and reducing power consumption.
• Wide Supply Voltage Range: Operates from ±15V down to a single 5V supply, making it suitable for both analog and digital applications.
• Logic Compatibility: Output is compatible with RTL, DTL, TTL, and MOS logic families, ensuring seamless integration into mixed-signal systems.
• High-Voltage Switching: Capable of driving loads up to 50V at currents as high as 50mA, enabling direct control of relays, lamps, and other high-voltage devices.
• Fast Response Time: Designed for quick switching, making it ideal for time-critical applications.
• Stable Operation: Excellent performance across temperature variations, with the LM211 rated for industrial temperatures and the LM111 for military-grade applications.

Applications

The LM311N is widely used in a variety of applications due to its robust design and versatile features. Below are some common use cases:

• Voltage Level Detection: Used in circuits to detect when a voltage crosses a predefined threshold, such as in battery monitoring systems.
• Analog-to-Digital Conversion: Acts as a critical component in ADC circuits, converting analog signals into digital logic levels.
• Relay and Lamp Drivers: Directly controls high-voltage devices like relays and lamps without requiring additional driver circuitry.
• Oscillators and Waveform Generators: Employed in square-wave and pulse generators due to its fast switching characteristics.
• Industrial Control Systems: Used in automation and control systems for signal conditioning and logic-level conversion.
• Power Supply Monitoring: Ensures stable operation by monitoring voltage levels in power supply circuits.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM311N under typical operating conditions (unless otherwise noted):

• Supply Voltage Range: ±15V (dual supply) or 5V to 30V (single supply)
• Input Offset Voltage: 2mV (max)
• Input Bias Current: 150nA (max)
• Input Offset Current: 20nA (max)
• Response Time: 200ns (typical)
• Output Saturation Voltage: 0.4V (at 4mA sink current)
• Output Voltage Swing: 50V (max)
• Output Current: 50mA (max)
• Operating Temperature Range: 0°C to +70°C (LM311N commercial grade)

Package Information

The LM311N is available in a standard 8-pin DIP (Dual In-line Package) configuration. Below are the key package details:

• Package Type: PDIP-8 (Plastic Dual In-line Package)
• Pin Count: 8
• Dimensions: 9.81mm x 6.35mm x 3.3mm (L x W x H)
• Pinout Configuration:
  • Pin 1: Output
  • Pin 2: Ground (GND)
  • Pin 3: VCC+ (Positive Supply)
  • Pin 4: Non-Inverting Input (+)
  • Pin 5: Inverting Input (-)
  • Pin 6: Balance
  • Pin 7: Balance/Strobe
  • Pin 8: VCC- (Negative Supply, if used)
• Mounting Style: Through-hole
• Operating Temperature: 0°C to +70°C (Commercial grade)

Conclusion

The LM311N is a highly versatile voltage comparator that combines low input current, wide supply voltage range, and high output drive capability. Its compatibility with multiple logic families and ability to interface directly with high-voltage loads make it an excellent choice for a wide range of applications, from industrial control systems to consumer electronics. The 8-pin DIP package ensures ease of integration into both prototyping and production environments. Whether used for precision voltage detection or robust switching applications, the LM311N delivers reliable performance across diverse operating conditions.