Abstract:
A filter is provided. The filter receives an input signal and generates an output signal according to the input signal. The filter includes an input network, a high-pass network, and an operational circuit. The first input network provides a first normal path for the input signal to generate a first normal signal. The first high-pass network provides a first high-pass path for the input signal to generate a first high-pass signal. The operational circuit has first and second input terminals. The polarity of the second input terminal is inverse to that of the first input terminal. The operational circuit receives the first normal signal by the first input terminal and the first high-pass signal by the second input terminal such that a subtraction operation is performed on the first normal signal and the first high-pass filter to accomplish a low-pass filtering operation for generating the output signal.
Abstract:
A sigma-delta modulator is provided for generating a digital output signal. The sigma-delta modulator is used to generate a digital output signal. The sigma-delta modulator includes a multi-stage loop filter and a quantizer. The multi-stage loop filter receives an analog input signal and generates an integrated output signal according to the analog input signal. The quantizer is coupled to the multi-stage loop filter. The quantizer receives the integrated output signal and quantizes the integrated output signal to generate the digital output signal. Different feed-forward paths of the sigma-delta modulator are available for different frequency bands.
Abstract:
An amplifier includes a front-end gain stage and an AC-coupled push-pull output stage. The AC-coupled push-pull output stage includes a first transistor, having a source, a drain and a gate, wherein the source of the first transistor is coupled to a first voltage level. The AC-coupled push-pull output stage further includes a second transistor, having a source, a drain and a gate, wherein the source of the second transistor is coupled to a second voltage level, the gate of the second transistor is coupled to the front-end gain stage, and the drain of the second transistor is coupled to the drain of the first transistor to form an output terminal of the amplifier. Further, the AC-coupled push-pull output stage includes an AC-coupled capacitor, which is a passive two terminal electrical component coupled between the front-end gain stage and the gate of the first transistor.
Abstract:
An amplifier includes a front-end gain stage and an AC-coupled push-pull output stage. The AC-coupled push-pull output stage includes a first transistor, having a source, a drain and a gate, wherein the source of the first transistor is coupled to a first voltage level; a second transistor, having a source, a drain and a gate, wherein the source of the second transistor is coupled to a second voltage level, the gate of the second transistor is coupled to the front-end gain stage, and the drain of the second transistor is coupled to the drain of the first transistor to form an output terminal of the amplifier; an AC-coupled capacitor, which is a passive two terminal electrical component coupled between the front-end gain stage and the gate of the first transistor;and a resistance component, coupling the gate of the first transistor to a bias voltage level.
Abstract:
An implementation of an operational amplifier circuit includes a first stage amplifier circuit, a second stage amplifier circuit and a first feedforward circuit. The first stage amplifier circuit is coupled to a first input node for receiving a first input signal and amplifying the first input signal to generate a first amplified signal. The second stage amplifier circuit is coupled to the first stage amplifier circuit for receiving the first amplified signal and amplifying the first amplified signal to generate a first output signal at a first output node. The first feedforward circuit is coupled between the first input node and the second stage amplifier circuit for feeding the first input signal forward to the second stage amplifier circuit.
Abstract:
The disclosure provides a voltage control device for controlling supply voltages of a power amplifier (PA). The voltage control device includes a first processing circuit to provide a first supply voltage to at least one driving stage amplifier of the PA, and a second processing circuit to provide a second supply voltage to an output stage amplifier of the PA. The first supply voltage is generated according to an average-power-tracking (APT) mechanism related to an average power level of a radio frequency (RF) signal transmitted by the PA.
Abstract:
A power supply configured to supply a modulated voltage to a power amplifier is shown. The power supply has an alternating current (AC) component generator, a direct current (DC) component generator, and a transition accelerator. The AC component generator generates an AC component of the modulated voltage according to an envelope tracking signal. The DC component generator generates a DC component of the modulated voltage according to the operational voltage range of the power amplifier. The transition accelerator is coupled to an output terminal of the DC component generator to speed up the transition of the modulated voltage.
Abstract:
A sigma-delta modulator is provided for generating a digital output signal. The sigma-delta modulator includes a multi-stage loop filter, a quantizer, and a digital-to-analog converter. The multi-stage loop filter receives an analog input signal and generates an integrated output signal according to the analog input signal. Each stage of the multi-stage loop filter includes a feedback network. The quantizer receives the integrated output signal and quantizes the integrated output signal to generate the digital output signal. The digital-to-analog converter receives the digital output signal and converts the digital output signal to a compensation signal. The digital-to-analog converter provides the compensation signal to a plurality of internal nodes in the feedback network of the last stage of the multi-stage loop filter.