A linear amplifier includes a pre-amplifier configured to amplify an input differential signal, a post-amplifier configured to amplify an output signal of the pre-amplifier, an amplitude detector configured to detect an amplitude of an output signal of the post-amplifier, and an output voltage corresponding to the detected amplitude, a comparator configured to control a tail current source of the pre-amplifier such that when the output voltage of the amplitude detector is less than or equal to a reference voltage, a tail current of the pre-amplifier is set to a constant value, and when the output voltage of the amplitude detector is larger than the reference voltage, the tail current is reduced to make the output voltage of the amplitude detector equal to the reference voltage.

Multi-mode broadband low noise amplifiers (LNAs) are disclosed herein. In certain embodiments, an LNA includes a first amplification stage and a second amplification stage having a lower gain than the first amplification stage. The LNA is operable in a plurality of operating modes including a first mode in which the first amplification stage and the second amplification stage operate in a cascade to amplify a radio frequency (RF) receive signal, and a second mode in which the first amplification stage amplifies the RF receive signal and the second amplification stage is bypassed.

A power amplifier includes a transistor, a temperature sensor and a filter. The transistor is used to receive a bias signal and amplify a radio frequency (RF) signal. The temperature sensor is arranged in proximity to the transistor, and is used to detect a temperature of the transistor to provide a voltage signal at a control node accordingly. The filter is coupled to the temperature sensor and is used to filter the voltage signal to generate a filtered voltage. The bias signal is adjusted according to the filtered voltage.

Multi-mode broadband low noise amplifiers (LNAs) are disclosed herein. In certain embodiments, an LNA includes a first amplification stage and a second amplification stage having a lower gain than the first amplification stage. The LNA is operable in a plurality of operating modes including a first mode in which the first amplification stage and the second amplification stage operate in a cascade to amplify a radio frequency (RF) receive signal, and a second mode in which the first amplification stage amplifies the RF receive signal and the second amplification stage is bypassed.

A power amplification system includes a Power Amplifier (PA) for amplifying an input RF signal. An adaptive bias circuit is configured to adaptively set a bias of the PA. The adaptive biasing circuit includes a gain expansion circuit, a gain compression circuit and a biasing circuit. The gain expansion circuit derives a gain-expansion control signal from the input RF signal. For a first sub-range of the input RF signal, the gain-expansion control signal has a larger dynamic range than the input RF signal. The gain compression circuit derives a gain-compression control signal from the input RF signal. For a second sub-range of the input RF signal having higher power levels than the first sub-range, the gain-compression control signal has a smaller dynamic range than the input RF signal. The biasing circuit sets the bias of the PA responsively to the gain-expansion control signal and the gain-compression control signal.

According to one embodiment, a signal processing circuit includes a first voltage setting circuit that sets a reference voltage on an input side of an isolator, a variable gain amplifier circuit that amplifies an output signal of the isolator, a DC offset adjustment circuit that adjusts an offset of the variable gain amplifier circuit, a second voltage setting circuit that sets a reference voltage on an output side of the isolator, and a control circuit that controls the DC offset adjustment circuit in response to a result of comparison of an output voltage of the variable gain amplifier circuit with an output voltage of the second voltage setting circuit.

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.

A signal amplifier device is provided to ensure the continuity of the gain of an amplifier. The signal amplifier device includes a main path and a sub path connected in parallel to the main path. A main path first amplifier circuit amplifies an input signal on the main path. A main path second amplifier circuit includes a common-gate transistor connected in series with an output of the main path first amplifier circuit without sharing a DC current. On the main sub path, the sub path amplifier circuit amplifies the input signal by using a gain lower than the maximum gain in the main path.

An apparatus for detecting a neural spike includes: a preprocessing circuit configured to remove a low-frequency component from a neural signal to form a low-frequency component removed neural signal, and amplify the low-frequency component removed neural signal; a comparing circuit configured to compare an output signal of the preprocessing circuit to a threshold signal; a merging circuit configured to merge spikes within a reference interval of an output signal of the comparing circuit into one peak, and to generate, based on the merging of the spikes, an output signal comprising pulses; and a counting circuit configured to count the pulses.

Wideband signal buffers that can be employed for mmWave (millimeter wave) communication are disclosed. One example signal buffer comprises a variable gain amplifier (VGA) that receives two control words and outputs a feedback signal, wherein both an amplitude and a phase of the feedback signal are based on the two control words and on a bias voltage; and a matching network comprising a first inductor that outputs the bias voltage, a second inductor, and a third inductor that receives the feedback signal from the VGA, and wherein the first, second, and third inductors are magnetically coupled to each other, wherein the signal buffer is configured to receive a RF (Radio Frequency) input and to generate a RF output from the RF input based on a transfer function of the signal buffer, wherein the transfer function is based at least in part on the feedback signal.