A Low Frequency Band Tunable Sinusoidal Test Stimulus for Audio Power Amplifier

• Main Authors: JHOU,SIN-YI, 周信毅
• Other Authors: LIN,CHUN-WEI
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/x67pa8

碩士 === 國立雲林科技大學 === 電子工程系 === 107 === Along with the advancement of technology, Class D audio amplifiers are also widely used in multimedia systems. By modulating the audio signal into a digital form, the power amplifier output is driven to have high efficiency, small size and low distortion. In order to verify and test the function of the audio amplifier in the system, we must design a sine wave test signal generation circuit built into the system to generate a test signal corresponding to the sound frequency band. However, the resolution of the class D amplifier is high, and the required test is required. The signal must have a corresponding quality, and the audio signal falls in the relatively low frequency band. In the circuit design of the processing signal, relatively large passive components are often needed, especially capacitors, and the demand may not be realized in the integrated circuit at all. in. Therefore, this study proposes a cost-effective adjustable sine wave oscillator design that accurately produces sine waves that can be received by the human ear. The adjustable sine wave oscillator is composed of a multiplying capacitor, a gain control oscillator and a voltage-current converter. The multiplying capacitor uses the amplifier gain in the feedback path to amplify the capacitive impedance placed therein, and multiplies the finite physical capacitance value. For a fairly large equivalent capacitor. The gain control oscillator adjusts the gain ratio of each amplifier in the oscillating circuit to form a different oscillating condition, thereby adjusting the frequency and gain of the sine wave generated by the oscillator. The voltage-current converter is a linear conversion circuit that converts the voltage control signal into a corresponding current signal, controls the bias state of the amplifier in the oscillator, and achieves the purpose of regulating the oscillator. The technique proposed in this paper is implemented in a 0.18μm CMOS process, using a physical capacitor of 122.4pF as a passive component, generating a 10-fold equivalent capacitance value via a multiplying capacitor, and designing a linear voltage-to-current converter at a voltage of 1 volt. The range of the bias current of the oscillator can be controlled to produce a gain ratio of 2 to 10 times, and a corresponding sine wave test signal with an oscillation frequency ranging from 40 Hz to 20 kHz is generated, which is sufficient to cover the audio range receivable by the human ear. Within this range, the total harmonic distortion of the sine wave test signal is less than -88dB and the frequency disturbance is less than 0.3%, which is accurate enough to provide a test audio amplifier.