LMC6041 CMOS Operational Amplifier

Overview

The LMC6041 is an ultra-low power CMOS operational amplifier designed for applications requiring minimal power consumption and exceptionally low input leakage current. With a typical input current of just 2 fA, this amplifier is ideal for high-impedance sensor interfaces and precision analog circuits. The device operates from a single supply voltage, with rail-to-rail output swing capability, making it suitable for battery-powered and portable applications.

Built using advanced CMOS technology, the LMC6041 combines low power operation with good ac performance and excellent dc accuracy. The amplifier's input common-mode range includes ground, allowing it to handle signals near the negative supply rail in single-supply configurations.

Key Features

• Ultra-low input bias current: 2 fA typical
• Single-supply operation: 3V to 15.5V
• Rail-to-rail output swing
• Low supply current: 24 µA typical
• Input common-mode range includes ground
• High voltage gain: 130 dB typical
• Low input offset voltage: 3 mV maximum
• Available in 8-pin PDIP, SOIC, and TO-99 packages
• Extended temperature range: -40°C to +85°C

Applications

The LMC6041's unique combination of features makes it suitable for a wide range of precision and low-power applications:

Sensor Interfaces

• pH and chemical sensors
• Photodiode amplifiers
• High-impedance transducer interfaces
• Capacitive sensor circuits

Portable and Battery-Powered Equipment

• Medical instrumentation
• Handheld test equipment
• Wireless sensor nodes
• Energy harvesting systems

Precision Circuits

• Integrators and sample-and-hold circuits
• Low-leakage current buffers
• High-impedance voltage followers
• Low-power active filters

Electrical Characteristics

All specifications are given for V+ = 5V, V- = 0V, TA = 25°C unless otherwise noted.

DC Characteristics

• Input Offset Voltage: 1 mV typical, 3 mV maximum
• Input Bias Current: 2 fA typical, 20 fA maximum
• Input Offset Current: 1 fA typical, 10 fA maximum
• Input Common-Mode Range: -0.3V to V+ - 1.5V
• Large-Signal Voltage Gain: 130 dB typical
• Supply Current: 24 µA typical, 40 µA maximum
• Power Supply Rejection Ratio: 90 dB typical

AC Characteristics

• Gain Bandwidth Product: 140 kHz typical
• Slew Rate: 0.04 V/µs typical
• Equivalent Input Noise Voltage: 30 nV/√Hz at 1 kHz
• Phase Margin: 60° typical

Output Characteristics

• Output Voltage Swing: 0V to V+ - 0.01V (RL = 100 kΩ)
• Short-Circuit Current: 20 mA typical
• Output Resistance: 150 Ω typical

Package Information

The LMC6041 is available in three package options to suit different application requirements:

8-Pin PDIP (Plastic Dual In-Line Package)

• Package Code: P
• Dimensions: 9.81 mm x 6.35 mm body
• Lead Pitch: 2.54 mm
• Operating Temperature: -40°C to +85°C

8-Pin SOIC (Small Outline Integrated Circuit)

• Package Code: D
• Dimensions: 4.90 mm x 3.91 mm body
• Lead Pitch: 1.27 mm
• Operating Temperature: -40°C to +85°C

TO-99 Metal Can Package

• Package Code: H
• Dimensions: 9.08 mm diameter
• Lead Configuration: 8 leads
• Operating Temperature: -40°C to +85°C

Design Considerations

Power Supply Bypassing

For optimal performance, a 0.1 µF ceramic bypass capacitor should be placed as close as possible to the power supply pin. In applications where the power supply impedance is high or where long power supply leads are used, a larger electrolytic capacitor (1-10 µF) may be required in parallel with the ceramic capacitor.

Input Protection

While the LMC6041 features built-in ESD protection, additional external protection may be required in applications where the input may be exposed to voltages beyond the supply rails. Series input resistors and clamping diodes can be used to protect the input stage.

PCB Layout Guidelines

• Minimize stray capacitance at the input pins
• Use guard rings around high-impedance inputs
• Keep output traces short to minimize capacitive loading
• Maintain proper grounding techniques to avoid ground loops

Conclusion

The LMC6041 operational amplifier offers an exceptional combination of ultra-low power consumption and minimal input leakage current, making it an ideal choice for precision applications requiring high input impedance and low power operation. Its rail-to-rail output capability and single-supply operation further enhance its suitability for battery-powered and portable applications. With multiple package options and robust performance characteristics, the LMC6041 provides designers with a versatile solution for challenging analog circuit requirements.