Microchip MCP6L71T-E/OT Single Op-Amp: Features and Application Circuits
The Microchip MCP6L71T-E/OT is a single general-purpose operational amplifier (op-amp) that offers an excellent balance of performance and low power consumption, making it a versatile choice for a wide range of analog circuit designs. Packaged in the tiny SOT-23-5, it is particularly suited for space-constrained and portable, battery-powered applications.
Key Features
This op-amp is defined by several critical characteristics that enable its broad application:
Low Power Consumption: With a typical quiescent current of just 20 µA, the device is engineered for battery-powered and portable equipment where extended operational life is paramount.
Low Offset Voltage: A maximum input offset voltage of 3 mV ensures higher accuracy in signal conditioning and precision measurement circuits.
Rail-to-Rail Input and Output: The capability to swing its inputs and output very close to the supply rails (VSS to VDD) maximizes the dynamic range in low-voltage systems, which is crucial when operating from a single supply as low as 1.8V.
Gain Bandwidth Product: At 50 kHz, it is optimized for amplifying low-frequency signals, such as those from sensors (temperature, pressure, etc.), effectively filtering out higher-frequency noise.
Extended Temperature Range: The ‘E’ grade suffix indicates operation over the industrial temperature range (-40°C to +125°C), ensuring reliability in harsh environments.
Application Circuits
The MCP6L71T-E/OT can be configured in numerous standard op-amp topologies. Two fundamental and highly useful circuits are detailed below.
1. Non-Inverting Amplifier
This circuit is ideal for applications requiring high input impedance and a gain greater than one, such as buffering a sensor signal.
Circuit Configuration: The input signal (VIN) is applied directly to the non-inverting input (pin 3). Negative feedback is established through a voltage divider (resistors R1 and R2) connected between the output (pin 1), the inverting input (pin 2), and ground.
Gain Calculation: The closed-loop voltage gain (A_V) is set by the resistor values: A_V = 1 + (R2 / R1).
Example: To achieve a gain of 10, select R1 = 10 kΩ and R2 = 90 kΩ. This setup provides a stable amplification of low-frequency sensor signals with minimal loading on the source.
2. Active Low-Pass Filter (1st Order)
Combining amplification with filtering is a common requirement. This circuit attenuates high-frequency noise while amplifying the desired low-frequency signal.
Circuit Configuration: This is built upon the non-inverting amplifier topology. A capacitor (C1) is added in parallel with feedback resistor R2.
Function: The capacitor's impedance decreases with increasing frequency, which reduces the circuit's gain at higher frequencies. This creates a low-pass filter characteristic.
Cutoff Frequency Calculation: The -3dB cutoff frequency (f_c) is determined by: f_c = 1 / (2π R2 C1).
Example: With R2 = 90 kΩ and C1 = 18 pF, the cutoff frequency is approximately 100 Hz. This is perfect for conditioning audio signals or removing noise from DC sensor outputs.
The Microchip MCP6L71T-E/OT stands out as an exceptional choice for designers seeking a low-power, precision op-amp in a miniature package. Its rail-to-rail capability and stability at low voltages make it a fundamental building block for modern analog design in portable, industrial, and consumer applications. Its simplicity and effectiveness in circuits like sensor interfaces and active filters underscore its utility.
Keywords:
Low-Power Op-Amp
Rail-to-Rail I/O
SOT-23-5
Sensor Signal Conditioning
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