Amplifier Mute Circuit With Progressive Gain Switching
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Solution Overview
Problem
Existing audio amplifiers face challenges in achieving inaudible mute mode due to parasitic capacitance that allows input signals to propagate during transitions between mute and play modes, leading to distorted outputs.
Innovation Solution
Implementing a plurality of pass gates in the amplifier circuit to progressively turn on/off during transitions between mute and play modes, reducing parasitic capacitance effects and minimizing signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single switch is used to transition between mute and play modes, then the circuit complexity is low, but signal distortion occurs during transitions due to parasitic capacitance
Solution Approach 1:
The single switch is divided into multiple switches (first switch, second switch, etc.) that operate in sequence during mode transitions. Each switch handles a portion of the total capacitance, allowing the transition to occur in steps rather than all at once, thereby reducing signal distortion while maintaining manageable circuit complexity
Solution Approach 2:
The first switch is activated before the second switch during mode transitions. This preliminary action allows the first switch to begin discharging or charging the parasitic capacitance early in the transition process, reducing the overall transition time and minimizing signal distortion before the second switch completes the transition
2Ease of operation
If voltage PM is ramped linearly during mode transitions, then the control is simple, but the transition time is prolonged causing distortion
Solution Approach 1:
The mode transition is achieved through periodic switching of multiple switches in a predetermined sequence rather than a continuous linear ramp. This periodic action allows the system to complete transitions faster by breaking the continuous voltage change into discrete switching events, reducing transition time and distortion while maintaining control simplicity through automated sequencing
3Reliability
If multiple switches are used to reduce distortion, then signal quality improves, but the device complexity increases
Solution Approach 1:
The capacitance management function is segmented across multiple switches that operate in sequence. Each switch handles a portion of the total parasitic capacitance, allowing the system to achieve low distortion through distributed switching rather than requiring a single complex switching mechanism, thereby balancing signal quality with manageable circuit complexity
Solution Approach 2:
The multiple switches are designed to perform the same fundamental function (switching) but at different stages of the transition process. This multi-functionality allows the system to achieve complex transition management through repeated application of a simple, well-understood switching mechanism, reducing overall system complexity while maintaining high signal quality
Data Source
AI summary
In an embodiment, an amplifier circuit includes a second stage that includes a first switch circuit including first and second terminals, a plurality of resistive elements coupled between the first and second terminals of the first switch circuit, and a plurality of switches configured to control an equivalent resistance between the first and second terminals of the first switch circuit. During play mode, the second stage has a gain between the input of the second stage and the output of the second stage of a first value. During a transition from mute mode to play mode, the amplifier circuit is configured to progressively increase the gain of the second stage from a second value to the first value. During a transition from play mode to mute mode, the amplifier circuit is configured to progressively decrease the gain of the second stage from the first value to the second value.