Amplifier Ramp-Up Sequencing to Eliminate Turn-On Pops and Clicks
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Solution Overview
Problem
Conventional operational amplifiers in inverting configurations experience pops or clicks due to non-uniform output currents, which existing designs have not fully mitigated.
Innovation Solution
A folded cascode amplifier design with a plurality of voltage rails, current sources, an input stage, an intermediate circuit, and a clamp, where the current sources and intermediate circuit are actuated in a specific sequence to manage output currents and eliminate pops or clicks by transitioning through class B and class AB amplifier modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a push-pull or folded cascode arrangement is used in the amplifier, then the amplifier can provide high gain and wide bandwidth, but non-uniform output currents are generated causing pops or clicks
Solution Approach 1:
The patent applies preliminary action by activating current sources before the intermediate circuit during amplifier turn-on. This sequencing ensures that output currents are established in advance and matched before the main amplification path is activated, preventing pops or clicks while maintaining high gain performance
Solution Approach 2:
The patent changes the operational parameters by transitioning through different amplifier modes (class B to class AB) during activation. By dynamically changing the conduction angle and bias conditions, the output currents are controlled to match closely, eliminating pops or clicks while preserving the high gain capability of the folded cascode architecture
2Object-generated harmful factors
If existing anti-pop circuits are applied, then some pop or click reduction is achieved, but the non-uniform output currents are not fully mitigated
Solution Approach 1:
The patent employs feedback mechanisms where the activation sequence of current sources and the intermediate circuit creates a self-regulating system. The output current matching is achieved through feedback control during the transition from class B to class AB mode, ensuring reliable operation and complete elimination of pops or clicks
Solution Approach 2:
The patent makes the amplifier operation dynamic by transitioning between class B and class AB modes during activation. This dynamic adjustment of operating parameters allows the system to optimize current matching in real-time, achieving both pop/click elimination and operational stability
Data Source
AI summary
To reduce pop or click during turn-on, a method and apparatus are provided. Initially, a plurality of current sources in the amplifier is actuated. The amplifier is transitioned from an off-state to an on-state in a class B amplifier mode by de-coupling each input node of an output stage of the amplifier from a voltage rail, and the amplifier is transitioned from the on-state in the class B amplifier mode to an on-state in a class AB amplifier mode by actuating at least a portion of an intermediate circuit in the amplifier.