Split-Supply Amplifier Output Stage for Leakage Suppression
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Solution Overview
Problem
In voltage regulator circuits, increasing the size of the pass device to support higher output current levels results in higher leakage current, which becomes significant at low load conditions or in low-power operating modes.
Innovation Solution
The implementation of an amplifier circuit with a split power supply, where the output stage operates at a power supply voltage with a magnitude less than the amplifier stage, and a feedback connection that drives the channel field potential of the output device to a voltage greater than the second power supply voltage, reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the size of the pass device is increased to support higher output current levels, then the output current capability is improved, but the leakage current increases
Solution Approach 1:
The amplifier is divided into two separate stages: a first amplifier stage operating at a first power supply voltage and a second amplifier stage operating at a second power supply voltage. The pass device is controlled by these two stages in a cascaded manner, allowing the device to be effectively segmented into two control domains. This segmentation enables the pass device to achieve high output current capability through the first stage while the second stage suppresses leakage current by operating at a different voltage level.
Solution Approach 2:
The invention changes the power supply voltage parameter by introducing two different power supply voltages (first power supply voltage and second power supply voltage) for controlling the pass device. The first amplifier stage operates at the first power supply voltage to enable high current output, while the second amplifier stage operates at the second power supply voltage to reduce leakage. This parameter change allows the same pass device to operate in two different modes simultaneously, resolving the contradiction between high current capability and low leakage.
2Power
If a single large pass device is used to provide high output current, then the output current capability is improved, but the leakage current becomes significant at low load conditions
Solution Approach 1:
The control of the single large pass device is segmented into two amplifier stages with different power supply voltages. The first amplifier stage provides the main drive signal for high current capability, while the second amplifier stage provides an additional control signal that adjusts the gate voltage to suppress leakage at low load conditions. This segmentation of control functions allows the pass device to maintain high current capability while minimizing harmful leakage effects.
Solution Approach 2:
The second amplifier stage receives feedback regarding the operating conditions of the pass device and adjusts its output accordingly. By monitoring the load conditions and adjusting the gate voltage through the second amplifier stage operating at a different power supply voltage, the system can dynamically suppress leakage current at low load conditions while maintaining high output current capability when needed.
Data Source
AI summary
An amplifier circuit and its method of operation reduce leakage in the output stage of the under no-load or low-load conditions. The amplifier circuit includes an amplifier stage that generates an output signal, an output stage including an output device, a pre-driver device coupled to a gate of the output device, and a feedback connection from the output device to the amplifier stage. A power supply rail of the amplifier is provided by a first power supply voltage, and the output signal of the amplifier stage is coupled to an input of the pre-driver device. A power supply rail of the output stage is provided by a second power supply voltage having a magnitude less than the first power supply voltage. An increased voltage magnitude at the output stage is compensated by driving a channel field potential of the output device above the second power supply voltage.