LM2902DTBR2G Quad Operational Amplifier: Key Features and Application Circuits

The LM2902DTBR2G is a monolithic quad operational amplifier designed to operate from a single power supply over a wide voltage range. It is part of the industry-standard LM2902 series, known for its cost-effectiveness and reliable performance in industrial, automotive, and consumer applications. This op-amp integrates four independent high-gain frequency-compensated amplifiers in a single package, making it an ideal solution for space-constrained PCB designs requiring multiple amplification stages.

Key Features

A primary advantage of the LM2902DTBR2G is its single-supply operation from 3V to 26V (or ±1.5V to ±13V with a dual supply). This wide range provides exceptional flexibility for various system voltages. The device features a low supply-current drain, which remains virtually constant across the entire supply voltage range. Each amplifier is internally frequency compensated for unity-gain stability, simplifying circuit design by eliminating the need for external compensation components.

Other notable characteristics include a low input bias and offset currents, along with a common-mode input voltage range that extends to the negative rail (ground in single-supply applications), enabling it to directly sense signals near ground. The output voltage also swings to within millivolts of the ground, a critical feature for single-supply, ground-referenced signal processing. The device is offered in a space-saving TSSOP-14 package, designated by the "DTBR2G" suffix, and is characterized for operation from -40°C to +125°C, making it suitable for harsh environments.

Application Circuits

1. Non-Inverting Amplifier:

This is a fundamental circuit for signal amplification. The input signal is applied to the non-inverting input (+). The closed-loop voltage gain is set by two resistors (R1 and R2) and is given by Av = 1 + (R2/R1). This configuration provides high input impedance, preventing loading on the signal source.

2. Active Low-Pass Filter:

By incorporating a resistor (R) and capacitor (C) in the feedback loop of the non-inverting amplifier, the circuit becomes a first-order active low-pass filter. The cutoff frequency (f_c) is determined by f_c = 1 / (2πRC). This circuit attenuates high-frequency noise while amplifying the lower-frequency signals of interest.

3. Voltage Follower (Unity-Gain Buffer):

In this configuration, the output is directly connected to the inverting input (-), creating a feedback factor of 1. The voltage follower provides a very high input impedance and a very low output impedance. It is exceptionally useful for isolating stages in a circuit, preventing a high-impedance signal source from being loaded down by a low-impedance load.

4. Differential Amplifier (Subtractor):

This circuit amplifies the difference between two input signals. Using four matched resistors, the output voltage is proportional to the voltage difference between the two inputs (Vout = (R2/R1) (V2 - V1)). It is perfect for rejecting common-mode noise, a common requirement in sensor interface applications, such as with bridge circuits like strain gauges or thermocouples.

5. Window Comparator:

Utilizing two of the four amplifiers, a window comparator circuit can detect when an input voltage falls inside or outside of a specific voltage "window" defined by two reference voltages. This is a crucial function in over-voltage and under-voltage protection circuits for power supplies and battery management systems.

ICGOODFIND: The LM2902DTBR2G stands out as a versatile, robust, and economical solution for a vast array of analog signal conditioning tasks. Its quad design maximizes functionality per unit area, while its wide supply range and rail-to-rail output swing make it indispensable for modern single-supply system design.

Keywords: Single-Supply Operation, Unity-Gain Stable, Quad Op-Amp, Low-Pass Filter, Differential Amplifier