Sigmastar Technology Ltd.

Zhong-Yuan Wan

Zhun Chen

Cheng-Qi Huang

Jian-Feng Xue

A wired transmitter includes a digital-to-analog converter (DAC) and a line driver. The DAC generates first output signals according to a digital code, wherein a first circuit in the DAC operates in a first voltage domain and a second circuit of the DAC operates in a second voltage domain, and an upper limit of the first voltage domain is lower than an upper limit of the second voltage domain. The line driver operates in the second voltage domain, and generates second output signals according to the first output signals. Each of the DAC and the line driver is implemented by transistors corresponding to the first voltage domain.

Wired transmitter with overvoltage protection

An audio player device includes a digital-to-analog converter (DAC), a startup circuit, a multiplexer and an output amplifier. The DAC converts audio data into a first signal and a second signal. The startup circuit gradually increases a level of a startup voltage according to a reference voltage during a predetermined period. The multiplexer outputs the startup voltage as a control voltage during the predetermined period, and switches to output the reference voltage as the control voltage after the predetermined period has elapsed. The output amplifier generates an audio signal according to the control voltage, the first signal and the second signal. The control voltage is used to set a common mode voltage of the output amplifier.

Audio player device and startup method thereof

A line driver includes a first resistive component, a second resistive component, an operational amplifier and an adjustable current mirror array circuit. A first terminal of the second resistive component and the first resistive component are coupled to a node, and a second terminal of the second resistive component is coupled to an output terminal. The operational amplifier receives a common mode voltage through the first resistive component, and generates a first signal and a second signal according to the common mode voltage and an input signal. The adjustable current mirror array circuit generates a first current to the node and a second current to the output terminal in response to the first and second signals, and adjusts a ratio of the second current to the first current in response to multiple control bits so as to set an output impedance of the output terminal.

Growing community of inventors

Shanghai, China

Zhong-Yuan Wan