Amplifier Circuit Phase Lead Current Oscillation

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Solution Overview

Problem

Existing negative feedback amplifier circuits face phase delays due to poles in the output amplifier circuit, leading to a high risk of oscillation, which is influenced by load capacitance and resistance conditions.

Innovation Solution

An amplifier circuit with a capacitor forming a signal propagation path to generate a phase lead current, alleviating phase delay and improving phase characteristics, thereby reducing the risk of oscillation in negative feedback circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a negative feedback amplifier circuit uses a common source amplifier configuration, then the amplifier can maintain a constant operating point, but phase delay occurs due to poles in the output amplifier circuit, increasing the risk of oscillation

Engineering Contradiction:

Improveoperating point stabilityVSAvoidoscillation risk

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent introduces a capacitor as an intermediary element connected between the source of the second transistor and ground. This capacitor acts as a mediator that generates a phase lead current, which compensates for the phase delay caused by the pole in the output amplifier circuit, thereby reducing oscillation risk while maintaining operating point stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters of the amplifier circuit by adding a capacitor, which modifies the frequency response and phase characteristics. This parameter change introduces a zero in the transfer function that compensates for the pole, improving phase margin and reducing oscillation tendency

Inventive Principle:

Principle #35Parameter changes

2Speed

If the load capacitance and load resistance are small, then the pole appears at a high frequency causing phase delay, but if they are large, the pole appears at a low frequency causing phase delay

Engineering Contradiction:

Improvepole frequencyVSAvoidphase delay

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies preliminary anti-action by introducing a capacitor that generates a phase lead current before the phase delay becomes problematic. This preemptive measure counteracts the phase delay effect regardless of whether the pole appears at high or low frequencies, ensuring stable operation across different load conditions

Inventive Principle:

Principle #9Preliminary anti-action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The proposed solution effectively alleviates phase delay in feedback voltages, enhancing phase characteristics and stabilizing negative feedback amplifier circuits, including voltage regulators, by using a capacitor to generate a phase lead current.

Implementation Method 1

a capacitor (114) configured to generate a phase lead current

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9800156B2Amplifier circuit and voltage regulator

Publication Date: 2017.10.24 ABLIC INC

AI summary

Provided are an amplifier circuit capable of improving phase characteristics, and a voltage regulator including the amplifier circuit. The amplifier circuit is configured to amplify an input voltage and to output the input voltage, and includes a current source, a first transistor having a gate to which the input voltage is applied, and a second transistor having a gate to which a voltage synchronous with the input voltage is applied, and a source connected to a capacitor.