Low-Power, Single Op Amp: Microchip MCP6L91T-E/OT Datasheet and Application Circuit Design

In the realm of modern electronics, the demand for low-power, high-performance analog components continues to grow, driven by portable, battery-powered, and energy-harvesting applications. The Microchip MCP6L91T-E/OT stands out as a quintessential solution in this space. This operational amplifier combines exceptionally low quiescent current with a compact SOT-23-5 package, making it an ideal choice for designs where power efficiency and board space are critical constraints.

A deep dive into the device's datasheet reveals its core strengths. Operating from a supply voltage range of 1.8V to 6.0V, the MCP6L91T is versatile enough for both single-cell lithium and two-cell alkaline/NiMH battery-powered systems. Its defining characteristic is an ultra-low typical quiescent current of 10 µA, which directly translates to extended battery life. Despite this minimal power draw, it does not sacrifice performance entirely, offering a gain bandwidth product of 50 kHz and a typical input offset voltage of 0.5 mV. This makes it suitable for a variety of signal conditioning tasks, including sensor amplification, filter circuits, and low-frequency signal processing where speed is not the primary concern. The op amp is also designed with rail-to-rail input and output operation, maximizing the dynamic range in low-voltage applications and ensuring the signal can swing very close to both power supply rails.

A fundamental application circuit for this op amp is a non-inverting amplifier, commonly used for sensor interface. For a circuit designed to amplify a small sensor signal (e.g., from a thermistor or photocell), the configuration is straightforward. The sensor is connected to the non-inverting input (V+). Two resistors, R1 and R2, set the closed-loop gain (Av = 1 + (R2/R1)). The low bias current of the MCP6L91T (typically 1 pA) means that very high-value resistors can be used to minimize power consumption further without introducing significant errors. Decoupling is crucial; a 0.1 µF ceramic capacitor should be placed as close as possible to the supply pin (VDD) and ground to ensure stability and reject power supply noise.

When designing the PCB for this IC, attention to detail is paramount. The device's high input impedance makes it susceptible to noise pickup. Therefore, keeping the input traces short, guarding sensitive nodes, and using a solid ground plane are essential practices. For applications requiring precise DC accuracy, the low input offset voltage is beneficial, though for the most demanding roles, the specific variant's offset should be checked.

ICGOOODFIND: The Microchip MCP6L91T-E/OT is a highly efficient and compact operational amplifier that excels in ultra-low-power applications. Its optimal blend of minimal current consumption, rail-to-rail capability, and sufficient bandwidth makes it a superior choice for extending battery life in portable sensor systems, medical devices, and remote data loggers without compromising on critical performance parameters.

Keywords: Low-Power Op Amp, MCP6L91T-E/OT, Rail-to-Rail, Quiescent Current, Sensor Amplification