An output signal can be free of any noise component generated from an amplifier disposed in a path, without degradation of the S/N ratio of the output signal. An amplifier includes: a first amplifier that is connected to an input node and generates a first intermediate signal; a feedback resistor that enables feedback of the first intermediate signal to the input node; an attenuator that receives the first intermediate signal and generates a second intermediate signal; a second amplifier that is connected to the input node and generates a third intermediate signal; a third amplifier that is connected to the input node and generates a fourth intermediate signal; and an adder that generates an output signal, using the second intermediate signal, the third intermediate signal, and the fourth intermediate signal.

A platform for audio and electronic music applications where the electronics are implemented as modules, and the modules mount in a cabinet with a common power supply and infrastructure. The platform addresses problems in electrical, mechanical, usability, and power distribution areas, and is suitable for guitar effects, synthesizers, studio equipment, and DJ gear.

An integrated circuit amplifier configurable to be either a programmable gain amplifier or an operational amplifier comprises two output blocks, one output block is optimized for programmable gain amplifier operation, and the other output block is optimized for operational amplifier applications. A common single input stage, input offset calibration and bias generation circuits are used with either amplifier configuration. Thus duplication of the input stage, offset calibration and bias generation circuits are eliminated while still selectably providing for either a programmable gain amplifier or operational amplifier configuration.

Devices, systems, and methods for multi-channel common-mode coupled alternating current (AC) gain amplifiers (MC-CM-AC Amp) are disclosed. The MC-CM-AC Amp can comprise a first operational amplifier including: a first non-inverting input port configured to be coupled to a first input signal, and a first inverting input port configured to be coupled to a first capacitor. The MC-CM-AC Amp can comprise a second operational amplifier including a second non-inverting input port configured to be coupled to a second input signal, and a second inverting input port configured to be coupled to a second capacitor. The MC-CM-AC Amp can comprise one or more gain-setting resistors configured to be coupled between the first capacitor and the second capacitor.

A signal amplification method includes receiving, from a capacitive sensor, a first input signal by a first control terminal of a first transistor, and a second input signal by a first control terminal of a second transistor. The method also includes producing a first output signal, including amplifying a first signal at a first load path terminal of the first transistor using a first inverting amplifier having an output coupled to a resistance network, and producing a second output signal, including amplifying a second signal at a first load path terminal of the second transistor using a second inverting amplifier having an output coupled to the resistance network. The method also includes feeding back the first and second output signal to a second load path terminal of the first transistor and to a second load path terminal of the second transistor via the resistance network according to a pre-determined fraction.

A device includes: a transistor having an input terminal configured to receive an input signal and to amplify the input signal; a bias current source configured to set a bias current of the input terminal of the transistor, the bias current source having a control input for receiving a control signal for selecting the bias current to have one of a plurality of selectable bias current levels; a bias resistance connected between the bias current source and the input terminal of the transistor; a bypass switch for selectively bypassing a first part of the bias resistance; and a control circuit for controlling the bypass switch to bypass the part of the bias resistance for a predefined time period in response to a change in the bias current level, and for controlling the bypass switch to stop bypassing the first part of the bias resistance after the predefined time period expires.

An example automatic gain control (AGC) circuit includes a base current-gain circuit having a programmable source degeneration resistance responsive to first bits of an AGC code word. The AGC circuit further includes a programmable current-gain circuit, coupled between an input and an output of the base current-gain circuit, having a programmable current source responsive to second bits of the AGC code word. The AGC circuit further includes a bleeder circuit, coupled to the output of the base current-gain circuit, having a programmable current source responsive to logical complements of the second bits of the AGC code word. The AGC circuit further includes a load circuit coupled to the output of the base current-gain circuit.

An amplifier includes a first circuitry, a second circuitry, and a plurality of amplifier circuitries. The first circuitry controls an enable signal. The second circuitry controls a bias signal. Circuitries which output signals are decided from among the plurality of circuitries based on the enable signal, and each of the circuitries which output the signals amplifies an input signal with a gain corresponding to the bias signal.

Techniques for controlling one or more audio amplifiers in or associated with a device coupled on a local area network are disclosed. An example playback device includes a processor, an amplifier, a network interface, and a memory. The memory includes a software module that, when executed by the processor, causes the playback device to: operate in a first power mode in which the amplifier consumes a first amount of power; while operating in the first power mode, determine that a defined time has passed since receiving, via the network interface, a specified type of data packet; and based on determining that the defined time has passed since receiving the specified type of data packet, transition from operating in the first power mode to operate in a second power mode in which the amplifier consumes a second amount of power, wherein the first amount of power is greater than the second amount of power.

A variable gain amplifier and an electronic apparatus. The variable gain amplifier includes a first transconductance stage circuit and a second transconductance stage circuit, where the first transconductance stage circuit includes a first amplifying circuit and a second amplifying circuit, the second transconductance stage circuit includes a third amplifying circuit and a fourth amplifying circuit, the first amplifying circuit and the fourth amplifying circuit form a differential input pair, and the second amplifying circuit and the third amplifying circuit form a differential input pair, and where each amplifying circuit of the first amplifying circuit, the second amplifying circuit, the third amplifying circuit, and the fourth amplifying circuit includes a plurality of parallel transistors, and bias control of the plurality of transistors is independent of each other.