Amplifier Startup Sequencing to Minimize Pop and Click Noise
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Solution Overview
Problem
Existing audio amplifiers suffer from turn-on and turn-off transients that produce noise, known as pop or click noises, which degrade their usability.
Innovation Solution
The amplifier circuit is designed with multiple operating states and a clock control circuit to manage the startup sequence, disabling output stages during charging to prevent noise, and using a bypass buffer and multi-stage amplifiers with feedback to stabilize voltages and minimize noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the amplifier output stage is enabled during capacitor charging, then the amplifier can immediately drive the speaker, but turn-on transients produce pop and click noise
Solution Approach 1:
The amplifier circuit performs preliminary charging of the bypass capacitor and voltage divider network before enabling the output stage. The clock control circuit sequences the startup so that capacitors are charged to their steady-state voltages first, then the output stage is enabled, preventing pop and click noise while achieving fast startup
2Object-generated harmful factors
If the amplifier output stage is disabled during capacitor charging, then pop and click noise is reduced, but the amplifier startup time increases
Solution Approach 1:
The clock control circuit uses periodic clock signals to sequence the startup process through defined states. The bypass capacitor charges during specific clock cycles when the output stage is disabled, then the output stage is enabled in subsequent cycles, achieving both noise reduction and acceptable startup time through time-multiplexed operation
3Object-generated harmful factors
If multiple operating states are implemented to control startup sequence, then turn-on transients are reduced, but device complexity increases
Solution Approach 1:
The clock control circuit acts as an intermediary that manages the complex multi-state startup sequence. It generates controlled signals to enable/disable the bypass buffer and output stage at appropriate times, simplifying the control logic while achieving precise sequencing of capacitor charging and output enablement to eliminate transients
Data Source
AI summary
In one embodiment, an amplifier circuit is formed to minimize pop and click noise on the outputs of the amplifier circuit. The amplifier circuit is configured to place an output stage of the amplifier circuit in a high impedance state to minimize the pop and click noise. In another embodiment, the amplifier circuit is configured to couple the inputs of two amplifiers together to minimize the pop and click noise.