Transconductor circuits with programmable tradeoff between bandwidth and flicker noise are disclosed. An example circuit includes an input port, an output port, a plurality of transistors, and a switch arrangement that includes a plurality of switches, configured to change coupling between the input port, the output port, and the transistors to place the transconductor circuit in a first or a second mode of operation. An input capacitance of the transconductor circuit operating in the first mode is larger than when the transconductor circuit is operating in the second mode. In the first mode, having a larger input capacitance results in a decreased flicker noise because the amount of flicker noise is inversely proportional to the input capacitance. In the second mode, having a smaller input capacitance leads to an increased flicker noise but that is acceptable for wide-bandwidth applications because wide-bandwidth signals may be less sensitive to flicker noise.

Circuit techniques for providing base-current cancellation of a bipolar junction transistor (BJT) differential pair that compensate for tail current noise and differential voltage transients without penalizing supply headroom.

Circuit techniques for providing base-current cancellation of a bipolar junction transistor (BJT) differential pair that compensate for tail current noise and differential voltage transients without penalizing supply headroom.

Apparatus and methods for biasing of low noise amplifiers (LNAs) are provided herein. In certain embodiments, an LNA includes at least one transistor that amplifies a radio frequency (RF) input signal, and a bias circuit including a current bias circuit that generates a bias current based on a reference current and a voltage bias circuit that generates at least one input bias voltage for the at least one transistor based on the bias current. The current bias circuit includes a first bias transistor that receives the reference current, a second bias transistor that generates the bias current, and an amplifier that controls a first bias voltage of the first bias transistor to match a second bias voltage of the second bias transistor.

Apparatus and methods for biasing of low noise amplifiers (LNAs) are provided herein. In certain embodiments, an LNA includes at least one transistor that amplifies a radio frequency (RF) input signal, and a bias circuit including a current bias circuit that generates a bias current based on a reference current and a voltage bias circuit that generates at least one input bias voltage for the at least one transistor based on the bias current. The current bias circuit includes a first bias transistor that receives the reference current, a second bias transistor that generates the bias current, and an amplifier that controls a first bias voltage of the first bias transistor to match a second bias voltage of the second bias transistor.

Aspects of the disclosure relate to devices, wireless communication apparatuses, methods, and circuitry implementing a low noise amplifier (LNA) with phase-shifting circuitry to achieve a continuous phase at the output of the LNA. One aspect is an amplifier including a high gain active path comprising active circuitry, and a low gain path comprising passive circuitry and phase-shifting circuitry. In one or more aspects, the phase-shifting circuitry is configured to shift a phase of an input signal within the low gain path such that the phase of an output signal outputted from the low gain path approximately matches a phase of an output signal outputted from the high gain active path. In at least one aspect, a gain of the high gain active path is higher than a gain of the low gain passive path.

An optical receiver can implement a transimpedance amplifier (TIA) to process received light using a closed loop optical pre-amplification. The optical receiver can use an average input value of the TIA to control an semiconductor optical amplifier (SOA) or pre-amplification as received average signal varies. The optical receiver can include a gain controller for the TIA that can measure the TIA swing to adjust the gain of the SOA to pre-amplify received light in a closed loop control configuration.

A class-D amplifier with good signal-to-noise ratio (SNR) performance is shown. The class-D amplifier includes a loop filter, a pulse-width modulation signal generator, a gate driver, a power driver, and a feedback circuit, which are configured to establish a closed amplification loop. The feedback circuit is configured to establish a feedback path. The class-D amplifier further includes a feedback breaker. The feedback breaker breaks the feedback path in response to conditions in which there no-signal information in the class-D amplifier.

Low-noise optical differential receivers are described. Such differential receivers may include a differential amplifier having first and second inputs and first and second outputs, and four photodetectors. A first and a second of such photodetectors are coupled to the first input of the differential amplifier, and a third and a fourth of such photodetectors are coupled to the second input of the differential amplifier. The anode of the first photodetector and the cathode of the second photodetector are coupled to the first input of the differential amplifier. The cathode of the third photodetector and the anode of the fourth photodetector are coupled to the second input of the differential amplifier. The optical receiver may involve two stages of signal subtraction, which may significantly increase noise immunity.

Low-noise optical differential receivers are described. Such differential receivers may include a differential amplifier having first and second inputs and first and second outputs, and four photodetectors. A first and a second of such photodetectors are coupled to the first input of the differential amplifier, and a third and a fourth of such photodetectors are coupled to the second input of the differential amplifier. The anode of the first photodetector and the cathode of the second photodetector are coupled to the first input of the differential amplifier. The cathode of the third photodetector and the anode of the fourth photodetector are coupled to the second input of the differential amplifier. The optical receiver may involve two stages of signal subtraction, which may significantly increase noise immunity.