Circuits, methods and devices are disclosed, related to fast turn-on of radio-frequency amplifiers. In some embodiments, an RF amplifier circuit includes an amplification path implemented to amplify an RF signal, where the amplification path includes a switch and an amplifier. In some embodiments, each of the switch and the amplifier are configured to be ON or OFF to thereby enable or disable the amplification path, respectively. In some embodiments, the RF amplifier circuit includes a compensation circuit coupled to the amplifier, where the compensation circuit is configured to compensate for a slow transition of the amplifier between its ON and OFF states resulting from a signal applied to the switch.

A differential amplifier circuit includes a differential pair including a first field-effect transistor (FET) and a second FET, a first current source that generates a current which flows in the first FET and the second FET, and an output circuit that outputs an output voltage corresponding to a difference between a gate voltage of the first FET and a gate voltage of the second FET in accordance with an operation of the differential pair. A back gate of the first FET is connected to a gate of the first FET, and a back gate of the second FET is connected to a gate of the second FET. A first feedback voltage corresponding to the output voltage is input to the gate of the second FET.

A receiver front end capable of receiving and processing intraband non-contiguous carrier aggregate (CA) signals using multiple low noise amplifiers (LNAs) is disclosed herein. A cascode having a common source configured input FET and a common gate configured output FET can be turned on or off using the gate of the output FET. A first switch is provided that allows a connection to be either established or broken between the source terminal of the input FET of each LNA. Further switches used for switching degeneration inductors, gate capacitors and gate to ground caps for each legs can be used to further improve the matching performance of the invention.

In optical receivers, extending the transimpedance amplifier's (TIA) dynamic range is a key to increasing the receiver's dynamic range, and therefore increase the channel capacity. Ideally, the TIA requires controllable gain, whereby the receiver can modify the characteristics of the TIA and/or the VGA to process high power incoming signals with a defined maximum distortion, and low power incoming signals with a defined maximum noise. A solution to the problem is to provide TIA's with reconfigurable feedback resistors, which are adjustable based on the level of power, e.g. current, generated by the photodetector, and variable load resistors, which are adjustable based on the change in impedance caused by the change in the feedback resistor.

Various transimpedance amplifier (TIA) arrangements for ultrasonic front-end receivers used in ultrasonic sensing applications are disclosed. An example TIA includes three common-source gain stages in a feedback loop with a common-gate stage. In some aspects, the TIA may include a level shifter configured to maintain the voltage at the gate of a transistor used to implement the first common-source gain stage of the feedback loop shifted by a certain amount with respect to the voltage at an input port to the TIA. In some aspects, at least portions of the TIA may be biased using bias currents that are configured to be process-, supply voltage-, and/or temperature-dependent. Various embodiments of the TIAs disclosed herein may benefit from one or more of the following advantages: reduced noise, reduced input impedance, reduced temperature coefficient of input impedance, and stability for a wide range of sensor frequencies.

An electronic circuit comprises an input stage, a gain stage operatively coupled to the input stage, a primary output stage operatively coupled to the gain stage, a replica output stage operatively coupled to the gain stage in parallel to the primary output stage, and a clock circuit. The clock circuit operates the electronic circuit in multiple phases including a sampling phase to disconnect the primary output stage and the replica output stage from the gain stage to obtain an offset voltage, an active phase to reconnect the primary output stage to apply the offset voltage to reduce an offset at the primary output stage, and an intermediate phase to first reconnect the replica output stage to the gain stage prior to the active phase.

Methods and systems for accurate gain adjustment of a transimpedance amplifier using a dual replica and servo loop is disclosed and may include, in a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, and a third TIA, each comprising a configurable feedback impedance, and a control loop, where the control loop comprises a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs: configuring a gain level of the first TIA by configuring its feedback impedance, configuring a gain level of the third TIA by configuring a reference current applied to an input of the first TIA, and amplifying a received electrical signal to generate an output voltage utilizing the third TIA. The reference current may generate a reference voltage at one of the inputs of the gain stage.

Neuromodulation systems in accordance with embodiments of the invention can use a feed-forward common-mode cancellation (CMC) path to attenuate common-mode (CM) artifacts appearing at a voltage input, thus allowing for the simultaneous recording of neural data and stimulation of neurons. In several embodiments of the invention, the feed-forward CMC path is utilized to attenuate the common-mode swings at V.sub.in,CM, which can restore the linear operation of the front-end for differential signals. In several embodiments, the neuromodulation system may utilize an anti-alias filter (AAF) that includes a duty-cycles resistor (DCR) switching at a first frequency f.sub.1, followed by a DCR switching at a second frequency f.sub.2. The AAF allows for a significantly reduced second frequency f.sub.2 that enables the multi-rate DCR to increase the maximum realizable resistance, which is dependent upon the frequency ratio f.sub.1/f.sub.2.

A power amplifier includes a main transistor configured to amplify an input signal and having characteristics of a drain current delay, a replica transistor having the same characteristics of the drain current delay as the characteristics of the main transistor, a temperature of the replica transistor changing in accordance with a temperature of the main transistor, and an envelope signal of the input signal being input to the replica transistor, an extraction circuit configured to extract a delay component due to the drain current delay from an output voltage of the replica transistor and an adder configured to add the delay component to a gate bias voltage to be applied to the main transistor so as to cancel out the drain current delay of the main transistor.

In optical receivers, extending the transimpedance amplifier's (TIA) dynamic range is a key to increasing the receiver's dynamic range, and therefore increase the channel capacity. Ideally, the TIA requires controllable gain, whereby the receiver can modify the characteristics of the TIA and/or the VGA to process high power incoming signals with a defined maximum distortion, and low power incoming signals with a defined maximum noise. A solution to the problem is to provide TIA's with reconfigurable feedback resistors, which are adjustable based on the level of power, e.g. current, generated by the photodetector, and variable load resistors, which are adjustable based on the change in impedance caused by the change in the feedback resistor.