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.

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.

Provided is a remote broadcast system including an audio amplifier activation device configured to turn on when a level of input sound via a smartphone mobile unit exceeds a threshold, a power source for an audio amplifier configured to amplify a signal of the input sound into a broadcast audio signal, and output the broadcast audio signal to a broadcast loudspeaker, the audio amplifier activation device being configured also to turn off the power source for the audio amplifier when the level of the input sound remains lower than the threshold for a predetermined time period. A broadcaster carrying a smartphone base unit can select a smartphone mobile station via the smartphone base unit, and establish a communication link between the smartphone base unit and the smartphone mobile station. With this, the broadcaster is allowed to broadcast evacuation guidance information even while evacuating.

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.

Split cascade circuits include multiple cascade paths coupled between voltage supply rails. Each cascade path includes a pair of controllable switches. A feedback path is provided for at least one of the cascade circuit paths. An active load circuit may also have a split cascade structure. Multiple-stage circuits, for implementation in Trans-Impedance Amplifiers (TIAs) or analog Receive Front-End modules (RXFEs), for example, include multiple stages of split cascade circuits.

A multi-gain LNA with inductive source degeneration is presented. The inductive source degeneration is provided via a tunable degeneration network that includes an inductor in parallel with one or more switchable shunting networks. Each shunting network includes a shunting capacitor that can selectively be coupled in parallel to the inductor. A capacitance of the shunting capacitor is calculated so that a combined impedance of the inductor and the shunting capacitor at a narrowband frequency of operation is effectively an inductance. The inductance is calculated according to a desired gain of the LNA. According to one aspect, the switchable shunting network includes a resistor in series connection with the shunting capacitor to provide broadband frequency response stability of the tunable degeneration network. According to another aspect, the LNA includes a plurality of selectable branches to further control gain of the LNA.

An amplifier circuit includes: an operational amplifier that includes two input terminals and an output terminal; a voltage-dividing resistor circuit electrically connected to the output terminal and that includes a voltage-dividing terminal that outputs a potential obtained by voltage-dividing a potential of the output terminal and a feedback resistor circuit electrically connected to the voltage-dividing terminal and one of the two input terminals. The voltage-dividing resistor circuit includes a plurality of resistors that each include terminals and a switch. The plurality of resistors includes a first resistor and a second resistor. The first resistor includes a terminal that corresponds to the voltage-dividing terminal. The switch switches, from a first terminal of the first resistor to a second terminal of the second resistor, the terminal that corresponds to the voltage-dividing terminal.

The present invention provides a circuitry applied to multiple power domains, wherein the circuitry includes a first circuit block and second circuit block, the first circuit block is powered by a first supply voltage of a first power domain, and the second circuit block is powered by a second supply voltage of a second power domain. The first circuit block includes a first amplifier and a switching circuit. The first amplifier is configured to receive an input signal to generate a processed input signal. When the second circuit block is powered by the second supply voltage, the switching circuit is configured to forward the processed input signal to the second circuit block; and when the second circuit block is not powered by the second supply voltage, the switching circuit disconnects a path between the first amplifier and the second circuit block.

A radio frequency (RF) summer circuit having a characteristic impedance Zo comprises first and second ports coupled by first and second resistances, respectively, to a junction. The circuit further comprises a series combination of a third resistance and a switch movable between open and closed positions and an amplifier having input and output terminals and operable in an off state and an on state wherein the series combination is coupled across the input and output terminals of the amplifier between the junction and a third port. The first resistance, second resistance, and the third resistance are all substantially equal to Z.sub.0/3. Further, when the switch is moved to the closed position and the amplifier is switched to the off state a passive mode of operation is implemented and when the switch is moved to the open position and the amplifier is switched to the on state an active mode of operation is implemented. The RF summer circuit develops a summed signal at the third port equal to a sum of signals at the first and second ports modified by one of first and second gain values.