D-Class Amplifier Voltage Adjustment for Optimal Op-Amp Bias
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Solution Overview
Problem
Conventional D-class amplifiers have operating characteristics limited by the supply voltage of the output stage, which affects the input operating voltage of the operational amplifier, restricting optimal performance.
Innovation Solution
A D-class amplifier circuit and audio amplifying method that includes an input impedance, operational amplifier, voltage-adjusting circuit, pulse-generating circuit, and drive circuit, where the input operating voltage of the operational amplifier is adjusted independently of the supply voltage, allowing for optimal operating voltage range determination based on various input pair forms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the supply voltage of the output stage is used to determine the input operating voltage of the operational amplifier, then the circuit structure is simple, but the input operating voltage is restricted and cannot achieve optimal operating characteristics
Solution Approach 1:
The power supply system is segmented into two independent parts: the first power voltage (VCC) for the operational amplifier and the second power voltage (VDD) for the output stage. This segmentation allows each part to operate independently with optimized voltage levels, resolving the contradiction between simple structure and optimal performance.
Solution Approach 2:
A voltage adjusting circuit is introduced as an intermediary between the second power voltage and the operational amplifier's power supply. This circuit adjusts the first power voltage based on the second power voltage, enabling the operational amplifier to operate at optimal voltage levels while maintaining independence from output stage supply variations.
2Device complexity
If the input operating voltage is fixed to half of the supply voltage of the operational amplifier, then the power supply configuration is simplified, but the operational amplifier cannot operate in its optimal voltage range for different input pair forms
Solution Approach 1:
The first power voltage is made dynamically adjustable through the voltage adjusting circuit, which can adaptively set the optimal operating voltage for the operational amplifier based on different input pair forms (e.g., BJT or MOSFET inputs), rather than being fixed at half the supply voltage.
Solution Approach 2:
The operating voltage parameter of the operational amplifier is changed from a fixed value (half supply voltage) to an adjustable parameter that can be optimized according to different input pair configurations, enabling the amplifier to achieve optimal performance for each specific form.
Data Source
AI summary
A circuit includes an input impedance, an operational amplifier, a voltage-adjusting circuit, a pulse-generating circuit, and a drive circuit. The input impedance is coupled to an input terminal of the operational amplifier, receives an input voltage, and outputs an input current. The operational amplifier is coupled to a first power voltage and outputs an amplified signal according to an input operating voltage and a feedback signal. The voltage-adjusting circuit adjusts the input operating voltage of the operational amplifier. The pulse-generating circuit generates a pulse width modulation signal according to the amplified signal. The drive circuit is coupled to a second power voltage and generates a driving signal according to the pulse width modulation signal. The feedback signal is correlated with the driving signal.