A radio frequency receiver and an automatic gain control method of the radio frequency receiver is presented. The radio frequency receiver includes an automatic gain control apparatus, a radio frequency component, and an analog to digital converter, where the automatic gain control apparatus further includes: an intensity calculator configured to calculate a relationship between an intensity representation parameter of digital data and a preset intensity threshold within a preset calculation time; and an automatic gain controller configured to compare the relationship calculated by the intensity calculator with a preset relationship threshold, and adjust a gain of the radio frequency component on radio frequency data according to a comparison result, so that an amplitude of the radio frequency data obtained after the gain adjustment is within a receiving range of the analog to digital converter.

A wideband amplifier includes a first stage and a second stage. The first stage includes a transconductance transistor driven by an input signal through an input transformer. The transconductance transistor couples to a cascode transistor forming an output node for the first stage. The second stage couples the output node from the first stage through an output transformer to drive an output transistor.

Technologies are provided for variable gain amplifiers (VGAs). An example VGA includes a resistor ladder including resistor legs coupled to first and second resistors; first differential switches connected to the resistor ladder and second differential switches connected to output nodes, a transistor in each of the first differential switches being coupled to an first electrical line interconnecting the first resistors and a different transistor in each of the first differential switches being coupled to a second electrical line interconnecting the second resistors; third differential switches connected to the resistor ladder and fourth differential switches connected to the output nodes, a transistor in each of the third differential switches being coupled to the first electrical line and a different transistor in each of the fourth differential switches being coupled to the second electrical line; and a pair of transistors respectively connected to the first differential switches and the third differential switches.

The present invention is directed to electrical circuits. In a specific embodiment, the present invention provides variable gain amplifier that includes an impedance ladder and a control circuit. The impedance ladder includes n switches configured in parallel. The control circuit includes a digital-to-analog converter and an amplifier. The control circuit generates n control signals for the n switches. There are other embodiments as well.

Example techniques may provide volume enhancements to a media playback system. An example implementation involves a first playback device in a first playback configuration playing audio at a first volume level and storing the first volume level in association with the first playback configuration. The first playback device receives instructions to change to a second playback configuration. Based on receiving the instructions, the first playback device joins a synchrony group with a second zone and adjusts the first playback device to play audio at a second volume level which is based on a volume level of a second playback device in the second zone. While in the second playback configuration, the first playback device receives instructions to change to the first playback configuration and, based on the instructions, leaves the synchrony group and adjusts the first playback device to play audio content at the stored first volume level.

A system that utilizes an amplified signal is disclosed that includes a plurality of first switches coupled to a plurality of first impedances. A plurality of second switches coupled to a plurality of second impedances. An amplifier having a first input coupled to the plurality of first switches and a second input coupled to the plurality of second switches. A leakage current offset source coupled to the first input of the amplifier, wherein the leakage current offset source cancels a leakage current component of a first current provided from the plurality of first switches to the first input.

A front-end amplifier circuit for receiving a biological signal includes a signal channel. The signal channel amplifies the biological signal to generate a detection current and includes a capacitive-coupled transconductance amplifier. The capacitive-coupled transconductance amplifier amplifies the biological signal with a transconductance gain to generate a first current.

A method can include modulating an amplified analog signal into a digital data stream, filtering the digital data stream with a first filter, generating gain control values associated with amplified analog signal based on the filtered data stream with the first filter and filtering the digital data stream with a second filter, and generating output digital values associated with the amplified analog signal based on the filtered data stream with the second filter. Corresponding systems and devices are also disclosed.

Disclosed are a two-stage audio gain circuit based on analog-to-digital conversion and an audio terminal. The two-stage audio gain circuit includes a PGA configured to receive an analog audio signal and perform programmable gain amplification processing on the received analog audio signal; an ADC configured to convert the analog audio signal after the programmable gain amplification processing into a digital audio signal and output the digital audio signal; a first AGC gain unit configured to perform a first AGC processing on the digital audio signal and output a first gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal; and a second AGC gain unit configured to perform a second AGC processing on the digital audio signal and output a second gain adjustment value to the PGA, for the PGA to perform gain adjustment on the received analog audio signal.

A fingerprint recognizing sensor with fast recognition, including: a substrate, a conductive plate, a passivation layer, a charging capacitor, a switch group, and an analog to digital (AD) converter; the conductive plate being arranged on the substrate; the passivation layer being arranged on the conductive pad for receiving a finger to detect a fingerprint; the switch group including a first switch and a second switch; the first switch controlling an input voltage to charge the charging capacitor; two ends of the second switch being electrically connected to the conductive plate and the first switch as well as the charging capacitor, respectively; the AD converter being electrically connected to the charging capacitor; where the second switch controls the charging capacitor to perform charge sharing for multiple times; and the AD converter outputs a fingerprint recognizing signal according to a residual voltage after the charge sharing.