LM3900N Quad Norton Operational Amplifier

Overview

The LM3900N is a quad Norton operational amplifier designed for single-supply operation, offering a wide voltage range and high performance in a compact package. Part of the LM2900 series, it features four independent, dual-input amplifiers with internal compensation, making it ideal for applications requiring large output voltage swings and low power consumption. The device utilizes a current mirror architecture to achieve non-inverting input functionality, enabling versatile use in AC amplification, signal conditioning, and waveform generation.

Key Features

• Wide Single-Supply Voltage Range: Operates from 4 VDC to 32 VDC or dual supplies (±2 VDC to ±16 VDC).
• Low Power Consumption: Supply current drain is independent of supply voltage.
• Low Input Bias Current: 30 nA typical, reducing errors in high-impedance circuits.
• High Open-Loop Gain: 70 dB ensures accurate signal amplification.
• Wide Bandwidth: 2.5 MHz unity-gain bandwidth supports high-frequency applications.
• Large Output Swing: (V_CC - 1) V_p-p output range maximizes dynamic performance.
• Internal Frequency Compensation: Stable at unity gain without external components.
• Output Short-Circuit Protection: Enhances reliability in fault conditions.

Applications

The LM3900N is suited for a broad range of analog and mixed-signal applications, including:

• AC Amplifiers: Small-signal amplification in audio and sensor interfaces.
• Active Filters: RC-based low-pass, high-pass, and band-pass designs.
• Waveform Generation: Triangle, squarewave, and pulse circuits at low frequencies.
• Tachometers and Speed Control: Frequency-to-voltage conversion in motor systems.
• Voltage Comparators: Threshold detection with adjustable hysteresis.
• Portable Devices: Battery-powered instrumentation due to low supply current.

Electrical Characteristics

Key specifications at T_A = 25°C, V_CC = 5 VDC unless otherwise noted:

DC Characteristics

• Input Offset Voltage: 2 mV (max)
• Input Bias Current: 30 nA (typ)
• Input Offset Current: 5 nA (typ)
• Common-Mode Rejection Ratio (CMRR): 70 dB (typ)
• Supply Current (Per Amplifier): 1.2 mA (typ)

AC Characteristics

• Unity-Gain Bandwidth: 2.5 MHz (typ)
• Slew Rate: 0.5 V/µs (typ)
• Output Resistance: 200 Ω (typ)

Large-Signal Performance

• Output Voltage Swing: V_CC - 1 V_p-p (typ)
• Short-Circuit Output Current: 20 mA (max)

Package Information

The LM3900N is available in two industry-standard packages:

14-Pin Dual-In-Line (DIP)

• Package Code: N14A
• Dimensions: 19.3 mm x 6.35 mm x 4.57 mm
• Pin Pitch: 2.54 mm
• Material: Molded Plastic

14-Pin Small Outline (SOIC)

• Package Code: M14A
• Dimensions: 8.65 mm x 3.9 mm x 1.5 mm
• Pin Pitch: 1.27 mm
• Material: Plastic, RoHS Compliant

Absolute Maximum Ratings

Stresses beyond these values may cause permanent damage:

• Supply Voltage (V_CC): 32 VDC
• Differential Input Voltage: ±32 V
• Input Voltage Range: -0.3 V to V_CC + 0.3 V
• Operating Temperature Range: 0°C to +70°C (Commercial)
• Storage Temperature Range: -65°C to +150°C
• Junction Temperature: 150°C

Schematic and Connection Diagrams

Refer to the manufacturer’s datasheet for detailed schematics and pinout diagrams. Key connections include:

• Non-Inverting Input: Current mirror-based design requires biasing.
• Output Stage: Class AB configuration for rail-to-rail swing.
• Compensation: Internal capacitor ensures stability.

Design Considerations

When using the LM3900N:

• Ensure proper decoupling with a 0.1 µF ceramic capacitor near the supply pins.
• For single-supply operation, bias inputs midway between rails for maximum swing.
• Minimize PCB trace lengths to reduce parasitic capacitance at high frequencies.
• Use series resistors (>1 kΩ) with capacitive loads to prevent oscillation.