LM725CN Operational Amplifier

Overview

The LM725CN is a precision operational amplifier designed for applications requiring low noise, low drift, and high accuracy in closed-loop gain. Part of the LM725/LM725A/LM725C family, this component is optimized for instrumentation and signal conditioning tasks where superior performance is critical. Its high common-mode rejection ratio (CMRR) and offset null capability make it particularly suitable for low-level signal amplification in demanding environments.

Manufactured using advanced semiconductor technology, the LM725CN provides stable operation across a wide temperature range while maintaining excellent electrical characteristics. The device is available in multiple package options to suit various PCB layout requirements.

Key Features

• High open-loop gain: 3,000,000 (typical)
• Low input offset voltage and drift
• Excellent common-mode rejection ratio (CMRR)
• Offset null capability for precision applications
• Wide operating voltage range
• Stable operation over extended temperature ranges
• Low noise characteristics
• High gain bandwidth product
• Available in multiple package options

Applications

The LM725CN is ideally suited for precision analog applications where signal integrity is paramount:

• Precision instrumentation amplifiers
• Medical equipment signal conditioning
• Strain gauge amplifiers
• Thermocouple amplifiers
• Data acquisition systems
• Analog computing circuits
• High-accuracy voltage regulators
• Test and measurement equipment
• Audio precision applications
• Sensor signal conditioning

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage: ±22V
• Input Voltage: ±15V
• Differential Input Voltage: ±30V
• Output Short-Circuit Duration: Continuous
• Operating Temperature Range: 0°C to +70°C (LM725CN)
• Storage Temperature Range: -65°C to +150°C

Typical Operating Characteristics

• Input Offset Voltage: 0.5mV (max)
• Input Offset Current: 2nA (max)
• Input Bias Current: 30nA (max)
• Open-Loop Gain: 3,000,000 (min)
• Common Mode Rejection Ratio: 120dB (min)
• Power Supply Rejection Ratio: 120dB (min)
• Slew Rate: 0.5V/μs (typ)
• Gain Bandwidth Product: 1MHz (typ)
• Input Voltage Noise: 10nV/√Hz (typ at 1kHz)

Package Information

LM725CN Package Options

• 8-Pin PDIP (N): Plastic Dual In-Line Package
• 8-Pin SOIC (D): Small Outline Integrated Circuit
• TO-99 Metal Can (H): Hermetically sealed package for high-reliability applications

Package Dimensions

8-Pin PDIP (N):

• Package Length: 9.81mm (max)
• Package Width: 6.35mm (max)
• Lead Pitch: 2.54mm
• Package Height: 3.3mm (max)

8-Pin SOIC (D):

• Package Length: 4.9mm (max)
• Package Width: 3.9mm (max)
• Lead Pitch: 1.27mm
• Package Height: 1.75mm (max)

Design Considerations

Power Supply Requirements

The LM725CN operates from dual power supplies ranging from ±5V to ±22V. For optimal performance, power supply bypass capacitors (0.1μF ceramic) should be placed as close as possible to the power supply pins.

Offset Null Adjustment

The device features offset null pins (pins 1 and 8) that allow for precise adjustment of the input offset voltage. A 10kΩ potentiometer connected between these pins with the wiper to the negative supply provides effective offset nulling capability.

Thermal Considerations

While the LM725CN has excellent thermal characteristics, proper PCB layout practices should be followed to ensure adequate heat dissipation, especially in high-gain applications or when driving low-impedance loads.

Typical Application Circuits

Precision Instrumentation Amplifier

The high CMRR and low noise characteristics of the LM725CN make it ideal for instrumentation amplifier circuits. A typical configuration uses three LM725CN devices to create a high-performance differential amplifier with adjustable gain.

Low-Noise Preamplifier

The device's low noise characteristics enable its use in sensitive preamplifier applications for audio or sensor signals. Careful attention to grounding and shielding is recommended for optimal noise performance.

Reliability and Quality

The LM725CN is manufactured under strict quality control procedures to ensure reliable operation in critical applications. The device undergoes extensive testing for:

• Electrical parameter verification
• Temperature cycling
• Burn-in testing (for certain reliability grades)
• Package integrity testing

Ordering Information

The LM725CN is available in various package options with different temperature grades:

• LM725CN: Commercial grade (0°C to +70°C), 8-Pin PDIP
• LM725CN/NOPB: Lead-free commercial grade, 8-Pin PDIP
• LM725CD: Commercial grade, 8-Pin SOIC
• LM725CH: Hermetic TO-99 metal can package