Abstract: A transceiver in a full duplex communication system includes a transmitting circuit coupled to a channel for transmitting a transmit signal to the channel, a cancellation signal generator coupled to the channel for generating a cancellation signal according to the transmit signal, and an echo cancellation device coupled to the transmitting circuit and the cancellation signal generator for attenuating an echo corresponding to the transmit signal with the cancellation signal.

Abstract: Bandgap reference circuits capable of preventing start failure. A voltage generation circuit generates a temperature-independent fixed voltage and comprises a current mirror, an operational amplifier, and first and second BJT transistors. A start-up circuit triggers the current mirror until at least one of the first and second BJT transistors operates in a forward-active region when powering on.

Abstract: The invention relates to an echo cancellation device for a full duplex communication system. The echo cancellation device utilizes a pull-up current source to increase the DC level, so as to improve the echo cancellation performance with avoiding signal distortion. And the pull-up current source used in the echo cancellation device can be implemented to a fixed current source or an adjustable current source.

Abstract: An optical storage apparatus, a preamplifier and a method of generating a tracking error signal. The optical storage apparatus includes a pickup head, a preamplifier, and a servo control. The pickup head generates radio frequency (RF) signals. The preamplifier includes a signal adjusting apparatus, a phase detector, a charge pump, and a circuit. The signal adjusting apparatus has input terminals for receiving the RF signals. At least two of the input terminals are substantially short-circuited when the optical storage apparatus is in a calibration mode. The phase detector generates control signals based on the phase differences between the radio frequency signals. The circuit generates current control signal based on the tracking error signal when the optical storage apparatus is in the calibration mode. The current magnitude of at least one of the current sources in the charge pump is determined according to the current control signal.

Abstract: A differential charge pump includes a differential charge pump unit, current adjusting device, and common mode voltage control circuit. The differential charge pump unit is used for generating a output voltage signal according to a pump-up signal and a pump-down signal. The current adjusting device is coupled to the differential charge pump unit for providing an adjusting current signal to the differential charge pump unit as the pump-up signal and pump-down signal are both enabled or disabled. The control circuit is coupled to the differential charge pump unit for outputting a feedback signal to the differential charge pump unit according to the output voltage signal.

Abstract: A high-to-low level shifter, coupled to a first external signal, for transforming the first external signal into an internal signal, wherein the first external signal substantially switches between a high-voltage-domain high potential and a high-voltage-domain low potential, the internal signal substantially switches between a low-voltage-domain high potential and a low-voltage-domain low potential. The high-to-low level shifter includes: an inverter, for generating a second external signal according to the first external signal, wherein the second external signal is inverse to the first external signal; and a level shifter, for generating the internal signal according to the first external signal and the second external signal.

Abstract: A transceiver in a full duplex communication system includes a transmitting circuit coupled to a channel for transmitting a transmit signal to the channel, a cancellation signal generator coupled to the channel for generating a cancellation signal according to the transmit signal, and an echo cancellation device coupled to the transmitting circuit and the cancellation signal generator for attenuating an echo corresponding to the transmit signal with the cancellation signal.

Abstract: An echo cancellation device in a full duplex communication system having a transmitter for transferring an near-end signal and a receiver for receiving a far-end signal includes a filter for generating a filtered signal according to the near-end signal; an echo canceller coupled to the filter for generating an echo cancellation signal according to the filtered signal; and at least one echo cancellation resistor coupled to the transmitter, the receiver, and the echo canceller; wherein the echo canceller further includes a pull-up current source for increasing a DC level of the echo canceller.

Abstract: A high-to-low level shifter, coupled to a first external signal, for transforming the first external signal into an internal signal, wherein the first external signal substantially switches between a high-voltage-domain high potential and a high-voltage-domain low potential, the internal signal substantially switches between a low-voltage-domain high potential and a low-voltage-domain low potential. The high-to-low level shifter includes: an inverter, for generating a second external signal according to the first external signal, wherein the second external signal is inverse to the first external signal; and a level shifter, for generating the internal signal according to the first external signal and the second external signal.

Abstract: A high-to-low level shifter, coupled to a first external signal, for transforming the first external signal into an internal signal, wherein the first external signal substantially switches between a high-voltage-domain high potential and a high-voltage-domain low potential, the internal signal substantially switches between a low-voltage-domain high potential and a low-voltage-domain low potential. The high-to-low level shifter includes: an inverter, for generating a second external signal according to the first external signal, wherein the second external signal is inverse to the first external signal; and a level shifter, for generating the internal signal according to the first external signal and the second external signal.

Abstract: An adjustable oscillating frequency function generator. The oscillating frequency of the function generator can be adjusted externally. The oscillation frequency is independent of the magnitude of the voltage source. Therefore, a pulse signal that withstands the voltage source signal can be provided.

Abstract: An adjustable oscillating frequency function generator. The oscillating frequency of the function generator can be adjusted externally. The oscillation frequency is independent of the magnitude of the voltage source. Therefore, a pulse signal that withstands the voltage source signal can be provided.

Abstract: The present invention relates to a phase detector with no dead zone comprising two detecting means and two control logic circuits. The phase-frequency detector employs the control logic circuits to proceed with reset operation of the detecting means such that the existence of a phase difference between the reference clock signal and the feedback clock signal prevents the misdetection of the up, down signals (output signal), and the up, down signals will not be simultaneously at "1".