LM324

LM324 - Low Power Quad Operational Amplifier

Overview

The LM324 series consists of four independent, high-gain, internally frequency compensated operational amplifiers designed specifically for single power supply operation. These amplifiers operate over a wide range of supply voltages with a very low current drain. The LM324 features a common mode input voltage range that includes ground, making it particularly suitable for single-supply applications.

This quad op-amp provides excellent performance for general purpose analog circuit applications while offering significant advantages in power-sensitive designs. The device maintains its specifications over the extended industrial temperature range (-40°C to +85°C), making it suitable for harsh environments.

Key Features

• Four internally compensated op amps in a single package
• Wide power supply range:
  • Single supply: 3V to 32V
  • Dual supplies: ±1.5V to ±16V
• Low supply current drain (700μA typical) - independent of supply voltage
• Common-mode input voltage range includes ground
• Large output voltage swing (0V to V+ - 1.5V)
• Low input bias current: 45nA typical
• Internal frequency compensation for unity gain
• Differential input voltage range equal to the power supply voltage
• Available in PDIP, SOIC, and TSSOP packages

Applications

The LM324's versatile characteristics make it suitable for numerous analog applications:

• Transducer amplifiers
• DC gain blocks
• Active filters
• Voltage followers
• Integrators
• Summing amplifiers
• Precision rectifiers
• Battery-powered instrumentation
• Signal conditioning circuits
• Industrial control systems
• Consumer electronics

Electrical Characteristics

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

Input Characteristics

• Input Offset Voltage: 2mV (typical), 7mV (maximum)
• Input Offset Current: 3nA (typical), 30nA (maximum)
• Input Bias Current: 45nA (typical), 250nA (maximum)
• Input Common Mode Voltage Range: 0V to VCC - 1.5V
• Input Resistance: 0.3MΩ (typical), 0.1MΩ (minimum)

Output Characteristics

• Large Signal Voltage Gain: 100V/mV (typical) at VCC = 15V, RL ≥ 2kΩ
• Output Voltage Swing: 0V to VCC - 1.5V (RL ≥ 10kΩ)
• Output Short Circuit Current: 40mA (typical)

Power Supply Characteristics

• Supply Voltage Range: 3V to 32V (single supply), ±1.5V to ±16V (dual supply)
• Supply Current (per amplifier): 700μA (typical), 1.2mA (maximum)
• Power Supply Rejection Ratio: 65dB (typical)

Dynamic Characteristics

• Gain Bandwidth Product: 1MHz (typical)
• Slew Rate: 0.5V/μs (typical)
• Unity Gain Bandwidth: 1MHz (typical)

Package Information

The LM324 is available in several industry-standard packages:

14-Pin PDIP (Plastic Dual In-line Package)

• Package Code: N
• Dimensions: 19.3mm x 6.35mm x 4.57mm
• Pin spacing: 2.54mm
• Operating temperature range: -40°C to +85°C

14-Pin SOIC (Small Outline Integrated Circuit)

• Package Code: D
• Dimensions: 8.65mm x 3.91mm x 1.58mm
• Pin spacing: 1.27mm
• Moisture Sensitivity Level (MSL): 1

14-Pin TSSOP (Thin Shrink Small Outline Package)

• Package Code: PW
• Dimensions: 5mm x 4.4mm x 1mm
• Pin spacing: 0.65mm
• Moisture Sensitivity Level (MSL): 1

Typical Performance Characteristics

The LM324 exhibits several important performance characteristics that designers should consider:

Open-Loop Frequency Response

The device shows a typical gain bandwidth product of 1MHz with a phase margin of approximately 60° when configured for unity gain. The open-loop gain remains above 80dB for frequencies below 100Hz.

Input Common Mode Range

The input common mode range extends from ground to approximately 1.5V below the positive supply rail. This characteristic enables ground-referenced input signals when operating from a single supply.

Output Swing vs Load Resistance

The output voltage swing approaches the supply rails more closely with higher load resistances. With RL = 10kΩ, the output typically swings within 1.5V of either rail.

Design Considerations

When designing with the LM324, several factors should be taken into account:

Power Supply Decoupling

While the LM324 is relatively immune to power supply noise, proper decoupling with 0.1μF ceramic capacitors placed close to the power supply pins is recommended, especially in high-noise environments.

Capacitive Load Driving

The LM324 can become unstable when driving capacitive loads greater than 100pF directly. For larger capacitive loads, a small series resistor (100Ω to 1kΩ) between the output and the capacitor improves stability.

Input Protection

Although the LM324 includes internal ESD protection diodes, additional external protection may be required in harsh environments or when inputs may exceed the supply rails.

Conclusion

The LM324 quad operational amplifier provides an excellent combination of performance, versatility, and cost-effectiveness for a wide range of analog applications. Its ability to operate from a single power supply while maintaining good electrical characteristics makes it particularly valuable in battery-powered and space-constrained designs. The device's robust design and wide operating temperature range ensure reliable performance in demanding industrial and commercial applications.