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LMV344IDG4 Application Field and Working Principle

The LMV344IDG4 is a low-dropout voltage regulator (LDO) designed to provide a regulated output voltage in a variety of linear-amplifier, instrumentation, OP amp, and buffer-amplifier applications. The LMV344IDG4, provides a precise output voltage over a wide operating temperature range. It belongs to a family of ultralow-power, low-dropout, micropower LDO regulators.

General Features of the LMV344IDG4

• Thermal Shutdown
• Low Dropout Voltage (V_DROP)
• Reverse- Current Protection
• Low Quiescent Current (I_Q)
• Low Noise
• High Power-Supply Rejection Ratio (PSRR)
• Low Output Noise
• High Accuracy

Applications of the LMV344IDG4

• Battery-Powered Electronics and Portable Equipment
• GPS Receivers and Controllers
• Mobile Phones and Pagers
• Notebook Computers
• Digital Still Cameras and Personal Digital Assistants
• Power Management in Disk Drives
• LCD Monitors

Working Principles of the LMV344IDG4

The LMV344IDG4 is an ultralow-power, low-dropout voltage regulator that utilizes a high performance Bias Tail current source topology which provides for a low temperature coefficient and low output noise. The operating principals of the LMV344IDG4 are critically dependent upon its design features. The schematic diagram of the LMV344IDG4 consists of three main sections including the input stage, the voltage reference, and the output stage.

Input Stage

The input stage consists of the differential amplifier and MOSFET pair which acts as a variable resistor, to sense and control the voltage across the sensing resistor. This sensing resistor is connected between the output node and the common-mode voltage. It is called the bias-tail current source in some aspects of its operation.

Voltage Reference

The voltage reference section is comprised of the operational amplifier and voltage reference components. The operational amplifier is used to control the voltage applied to the LMV344IDG4\'s reference terminal. This reference voltage is the voltage the LMV344IDG4 must maintain at its output node. Once the voltage is set, the operational amplifier controls the voltage across the sensing resistor, maintaining the correct reference voltage.

Output Stage

The output stage consists of the error amplifier, MOSFET pass transistor, and power transistor. The power transistor is connected between the output node of the LMV344IDG4 and the output node of the regulator. The error amplifier senses the voltage across the output node with the feedback voltage and amplifies the difference between the two. The error amplifier is then used to control the gate voltage of the MOSFET pass transistor, thus controlling the current flow and setting the output voltage.

Conclusion

The LMV344IDG4 is an ultralow-power, low-dropout voltage regulator that can be used in various linear-amplifier, instrumentation, op amp, and buffer-amplifier applications. Its superior features include high-power supply rejection ratio, low-dropout voltage, low-noise operation, and low quiescent current draw. Its main components include the input stage, voltage reference, and output stage.

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