Class AB Amplifier Startup Sequencing to Eliminate Pop Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Class AB amplifiers often experience output gate oscillations resulting in pops or clicks, which existing designs have not adequately addressed.
Innovation Solution
The apparatus includes an input stage with biasing circuitry, a control amplifier stage with current sources and transistors, and an output stage, utilizing a digital controller to actuate the control circuit after a bias point has settled, and employing capacitors to provide a linear ramp for controlled transistor turn-on, thereby reducing pops or clicks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amplifier stages are turned on quickly to improve response time, then productivity is improved, but output gate oscillations occur resulting in pops or clicks
Solution Approach 1:
The patent applies preliminary action by implementing a startup sequence where the input stage is activated first to establish a stable bias point, and only after this stabilization does the control circuit enable the control amplifier and output stages. This sequential activation prevents oscillations and pops/clicks that would occur if all stages were turned on simultaneously or in reverse order, thereby resolving the contradiction between fast response time and elimination of harmful output artifacts.
2Productivity
If the transistor is turned on rapidly to improve switching speed, then productivity is improved, but oscillations in output gate voltages occur
Solution Approach 1:
The control circuit is designed to enable the control amplifier stage only after the input stage has settled to a stable bias point. This preliminary stabilization of the bias conditions before activating the switching transistors ensures that when the transistors do switch rapidly, the output gate voltages remain stable and oscillation-free, thus resolving the contradiction between switching speed and voltage stability.
3Productivity
If all amplifier stages are actuated simultaneously to reduce startup time, then productivity is improved, but pops or clicks are generated
Solution Approach 1:
The patent implements a staged activation sequence where the input stage is activated first as a preliminary step to establish stable bias conditions. Only after this preliminary stabilization does the control circuit activate the control amplifier and output stages. This sequential approach eliminates pops and clicks caused by simultaneous activation while maintaining minimal startup time, thus resolving the contradiction between startup speed and elimination of harmful artifacts.
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 solution effectively eliminates pops or clicks by ensuring a controlled and smooth turn-on of the amplifier stages, resulting in reduced oscillations and improved output signal quality.
Implementation Method 1
a capacitor that is coupled to the control electrode of the transistor, wherein the capacitor is charged by the current source to provide a linear ramp for voltage on the capacitor
Data Source
AI summary
A method for actuating an amplifier to generally eliminate a pop is provided. Accordingly, a plurality of current sources is actuated in an input stage, and a plurality of bias voltages are applied to the input stage. After a predetermined period after the step of applying a plurality of bias voltages to the input stage and the step of actuating a plurality of current sources in an input stage, a control circuit is actuated, and a transistor within a control amplifier stage is turned on at a predetermined rate.