A number of field effect transistor circuits include voltage controlled attenuators or voltage controlled processing circuits. Example circuits include modulators, lower distortion variable voltage controlled resistors, sine wave to triangle wave converters, and or servo controlled biasing circuits.

An aspect includes a filtering method including operating a first filter to filter a first input signal to generate a first output signal; operating a second filter to filter a second input signal to generate a second output signal; and selectively coupling at least a portion of the second filter with the first filter to filter a third input signal to generate a third output signal. Another aspect includes a filtering method including operating switching devices to configure a filter with a first set of pole(s); filtering a first input signal to generate a first output signal with the filter configured with the first set of pole(s); operating the switching devices to configure the filter with a second set of poles; and filtering a second input signal to generate a second output signal with the filter configured with the second set of poles.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.

A variable-gain amplifier includes two amplification and attenuation branches, and first and a second resistive elements that are coupled between the two branches. Each branch includes a voltage follower stage and a configurable amplification stage. The voltage follower stages are intended to receive a differential signal and are configured to deliver, via the first resistive element, an intermediate differential current signal. The amplification stages are intended to receive the intermediate differential current signal and a digital control word, and are configured to deliver, via the second resistive element, an output differential voltage signal depending on the value of the digital control word.

Described herein are systems and methods that can adjust the performance of a transimpedance amplifier (TIA) in order to compensate for changing environmental and/or manufacturing conditions. In some embodiments, the changing environmental and/or manufacturing conditions may cause a reduction in beta of a bipolar junction transistor (BJT) in the TIA. A low beta may result in a high base current for the BJT causing the output voltage of the TIA to be formatted as an unusable signal output. To compensate for the low beta, the TIA generates an intermediate signal voltage, based on the base current and beta that is compared with the PN junction bias voltage on another BJT. Based on the comparison, the state of a digital state machine may be incremented, and a threshold base current is determined. This threshold base current may decide whether to compensate the operation of the TIA, or discard the chip.

According to one embodiment, in a semiconductor integrated circuit, the second circuit samples an amplitude of the output second signal at a plurality of timings every given cycle in a period corresponding to a second period of the pattern. The second circuit controls a parameter relating to the frequency characteristic for the first circuit according to a first magnitude relation and a second magnitude relation. The first magnitude relation is a relation between an absolute value of a first amplitude and a first threshold. The first amplitude is an amplitude sampled at a first timing among the plurality of timings. The second magnitude relation is a relation between an absolute value of a second amplitude and the first threshold. The second amplitude is an amplitude sampled at a second timing. The second timing is a timing after the first timing among the plurality of timings.

Embodiments of methods and systems for gain control in a communications device are described. In an embodiment, a method for gain control in a communications device involves detecting a change in an amplification gain that is applied to an analog signal in the communications device and compensating for the change in the amplification gain by manipulating an amplitude of a digital signal that is converted from the analog signal. Other embodiments are also described.

The detection matrix for an Orthogonal Differential Vector Signaling code is typically embodied as a transistor circuit with multiple active signal inputs. An alternative detection matrix approach uses passive resistor networks to sum at least some of the input terms before active detection.

This application relates to ADC circuitry. An ADC circuit (200) has first and second conversion paths (201a, 201b) for converting analogue signals to digital and is operable in first and second modes. In the first mode, the first and second conversion paths are connected to respective first and second input nodes (202a, 202b) to receive and convert full scale first and second analogue input signals (Ain1, Ain2) to separate digital outputs (Dout1, Dout2). In the second mode, the first and second conversion paths are both connected to the first input node (202a), to convert the first analogue input signal (Ain1) to respective first and second digital signals, and the first and second conversion paths are configured for processing different signal levels of the first analogue input signal. A selector (207) select the first digital signal or the second digital to be output as an output signal based on an indication of amplitude of the first analogue input signal.

A digital radio-frequency (RF) circuitry is disclosed. In one aspect, the circuitry includes a digitally controlled amplifier configured to receive an RF input signal and a digital control signal, and to output an amplitude controlled output signal. The digitally controlled amplifier includes one or more common-source amplifying unit cells. A respective common-source amplifying unit cell includes a sources node connected to a switching circuitry controllable by the digital control signal so as to activate or deactivate the common-source amplifying unit cell. The switching circuitry comprises a first switch configured to connect the source node with a first power supply node and a second switch configured to connect the source node with a second power supply node when activating and deactivating, respectively, the common-source amplifying unit cell.