A high-linear amplifier receives, from an input bandpass filter, input signals including weak process signals and strong interference signals, amplifies the input signals, and transmits the amplified signals to an output bandpass filter. The high-linear amplifier includes a transistor and a feedback circuit that stabilizes the operating current of the transistor. The operating current includes the direct-current and low-frequency output signal currents of the transistor. The feedback circuit includes an interference detector that rectifies a portion of the high-frequency output signals of the transistor and extends the linear range of the high-linear amplifier. An interference indicator unit alerts an operator to the presence of excessively high levels of interference before the high-linear amplifier enters the non-linear mode. Amplified signals rejected by the output bandpass filter are reflected back to the high-linear amplifier stage. A directional coupler prevents the reflected signals from disrupting the operation of the interference detector.

An apparatus includes a differential amplifier. The differential amplifier includes a first side circuit configured to receive a first input signal, a second side circuit configured to receive a second input signal, and a resonant tank circuit coupled between the first and second side circuits. A first capacitor and first switch may be provided in series between a source and drain of a cascode transistor. A second capacitor and second switch may be provided in series between a source and drain of an input transistor. A method includes receiving a first input signal by a first side circuit, receiving a second input signal by a second side circuit, controlling a resource of a resonant tank circuit, and outputting an output signal according to the first and second input signals. The resource of the resonant tank circuit may be controlled according to a transmission mode, frequency band, or both.

There is provided an operational amplifier which is operable as well when an operating voltage decreases without creating a range where a circuit would not operate or reducing circuit gain. High-pass filters 102-105 provide output signals therefrom to bias-set input nodes of differential amplifiers Gm1-Gm4 to a potential within a common-mode range in which the respective differential amplifiers Gm1-Gm4 are operable. In this manner, the respective differential amplifiers Gm1-Gm4 can be operated effectively regardless of the possible decrease in a supply voltage, enabling normal amplifying operation. In addition, reduction in gain due to the reduced operational voltage is avoided. Therefore, it is preferably applicable to the application where digital and analog circuits are loaded together on the same IC chip. When a high-pass filter is required at each input side of two- or more-stage differential amplifiers, a phase compensation method utilizing multiple paths is provided for a lower range of a phase margin created at the low frequency side, enabling normal amplitude operation.

There is provided an amplifier device for a CATV network comprising a first amplifier element for upstream signals and a second amplifier element for downstream signals, wherein the first and second amplifier elements are disposed between first and second directional couplers. The combined isolation of the first and second directional couplers is greater than the sum of the gain of the first and second amplifier elements. The first directional coupler has one port attached to an input of the downstream amplification element and one port attached to an output of an upstream amplification element (38) and the second directional coupler has one port attached to an output of the downstream amplifier and one port attached to an input of the upstream amplifier.

A power amplifier circuit includes a differential amplifier circuit configured to amplify a radio-frequency signal, a transformer disposed on an output side with respect to the differential amplifier circuit and including a primary winding and a secondary winding, and a dispersion circuit coupled to a midpoint of the primary winding of the transformer and configured to operate as an adjustment circuit. The dispersion circuit is configured to adjust, based on a supply voltage controlled in accordance with the envelope of the radio-frequency signal, a bias (bias current or bias voltage) to be supplied to the differential amplifier circuit.

A high-linear amplifier receives, from an input bandpass filter, input signals including weak process signals and strong interference signals, amplifies the input signals, and transmits the amplified signals to an output bandpass filter. The high-linear amplifier includes a transistor and a feedback circuit that stabilizes the operating current of the transistor. The operating current includes the direct-current and low-frequency output signal currents of the transistor. The feedback circuit includes an interference detector that rectifies a portion of the high-frequency output signals of the transistor and extends the linear range of the high-linear amplifier. An interference indicator unit alerts an operator to the presence of excessively high levels of interference before the high-linear amplifier enters the non-linear mode. Amplified signals rejected by the output bandpass filter are reflected back to the high-linear amplifier stage. A directional coupler prevents the reflected signals from disrupting the operation of the interference detector.

A neuron recording system was provided. By using the gain-boosted topology, the amplifier input impedance can be increased while simultaneously reducing the noise. The system can be configured to record local field potentials (LFPs) and neuron spikes, respectively, with low-power consumption. With the flexible digital controller module (DCM), any subset of the recording channels can be activated for recording with independent sampling rate at each channel. A wireless interface to transmit recorded neuron data and an on-chip neuron processor to perform real-time signal processing can be incorporated in the system.

An output matching circuit includes: a converter electrically connected to an output end of a power amplifier element to convert an impedance of the output end to an impedance higher than the impedance of the output end by magnetic coupling; and a first filter circuit electrically connected between the output end of the power amplifier element and the converter to make a short circuit in a frequency band different from a predetermined transmission frequency band.

A filter combiner for a Doherty amplifier includes a first port with an impedance of Z0 configured to be connected to an output of a carrier amplifier; a second port with an impedance of Z0.Math.r/(1+r) configured to be connected to a load; a third port with an impedance of Z0.Math.r/(1+r) configured to be connected to a peak amplifier, wherein r is a power ratio for the carrier amplifier to the peak amplifier; and a fourth port with an impedance of Z0 configured to be connected to an output port of the Doherty amplifier. The first port is connected to the second port via a first network that is a lowpass filter and to the third port via a second network that is a lowpass filter which is configured to operate as a band stop filter upon loading the input or the output of the second network with a high impedance when the peak amplifier is off. The third port is connected to the fourth port via a third network that is a lowpass filter configured to operate as a band stop filter upon loading the input or the output of the second network with a high impedance when the peak amplifier is off. The fourth port is connected to the second port via a fourth network that is a lowpass filter.

A power amplification circuit includes first wiring supplied with a first signal having a first frequency, second wiring supplied with a second signal having a second frequency that differs from the first frequency, a first amplification circuit that amplifies the first signal supplied through the first wiring and supplies a first amplified signal to the second wiring, and a second amplification circuit that amplifies the signal supplied through the second wiring and outputs a second amplified signal.