Methods and devices addressing design of reconfigurable wideband LNAs to meet stringent gain, noise figure, and linearity requirements with multiple gain modes are disclosed. The disclosed teachings can be used to reconfigure RF receiver front-end to operate in various applications imposing stringent and conflicting requirements, such as 5G NR radios. Wideband and narrowband input and output matching with gain modes using a combination of the same hardware and a switching network are also disclosed.

Amplifiers, amplification circuits, and phase shifters, for example, for flexibly adjusting an output phase to thereby meet a requirement of a constant phase on a link in a communications field, are provided. In one aspect, an amplifier includes first, second, and third MOS transistors. The first MOS transistor includes a gate separately coupled to a signal input end and a bias voltage input end, a source coupled to a power supply, and a drain separately coupled to sources of the second and third MOS transistors. A drain of the third MOS transistor is coupled to a ground, and a drain of the second MOS transistor is coupled to a signal output end. The bias voltage input end is configured to receive a bias voltage to adjust a phase difference between an input signal at the signal input end and an output signal at the signal output end.

An automatic gain control circuit of a transimpedance amplifier includes a transimpedance amplifier TIA1, a transimpedance amplifier TIA2, an NMOS transistor Q1, an NMOS transistor Q2, an error amplifier U3, and a bias current source Ib. An input terminal and an output terminal of the transimpedance amplifier TIA1 are connected to a drain and a source of the NMOS transistor Q1, respectively. An input terminal and an output terminal of the transimpedance amplifier TIA2 are connected to a drain and a source of the NMOS transistor Q2, respectively. An output terminal of the bias current source Ib is connected to a positive input terminal of the error amplifier U3 and the drain of the MOS transistor Q2.

Apparatus and methods for vector modulator phase shifters are provided. In certain embodiments, a phase shifter includes a quadrature filter that filters a differential input signal to generate a differential in-phase (I) voltage and a differential quadrature-phase (Q) voltage, an in-phase variable gain amplifier (I-VGA) that amplifies the differential I voltage to generate a differential I current, a quadrature-phase variable gain amplifier (Q-VGA) that amplifies the differential Q voltage to generate a differential Q current, and a current mode combiner that combines the differential I voltage and the differential Q voltage to generate a differential output signal. A phase difference between the differential output signal and the differential input signal is controlled by gain settings of the I-VGA and the Q-VGA.

Described herein are variable gain amplifiers and multiplexers that embed programmable attenuators into switchable paths to provide variable gain for individual amplifier inputs. The variable gain for an individual input is provided using a amplification stage that is common for each input of the amplifier. A variable attenuation is provided for individual inputs through a combination of a band selection switch and an attenuation selection branch. The attenuation can be tailored for individual inputs and can depend on a gain mode of the amplifier.

Disclosed herein are signal amplifiers that provide impedance adjustments for different gain modes. The impedance adjustments are configured to result in a constant real impedance for an input signal at the amplifier. The amplifiers include a scalable impedance adjustment circuit that adjusts inductance and/or a device width to compensate for changes in the total impedance presented to an input signal. By providing impedance adjustments, the amplifiers reduce losses and improve performance by improving impedance matching over a range of gain modes.

Methods and devices addressing design of reconfigurable wideband LNAs to meet stringent gain, noise figure, and linearity requirements with multiple gain modes are disclosed. The disclosed teachings can be used to reconfigure RF receiver front-end to operate in various applications imposing stringent and conflicting requirements, such as 5G NR radios. Wideband and narrowband input and output matching with gain modes using a combination of the same hardware and a switching network are also disclosed.

According to one embodiment, a low noise amplifier (LNA) circuit includes a first stage which includes: a first transistor; a second transistor coupled to the first transistor; a first inductor coupled in between an input port and a gate of the first transistor; and a second inductor coupled to a source of the first transistor, where the first inductor and the second inductor resonates with a gate capacitance of the first transistor for a dual-resonance. The LNA circuit includes a second stage including a third transistor; a fourth transistor coupled between the third transistor and an output port; and a passive network coupled to a gate of the third transistor. The LNA circuit includes a capacitor coupled in between the first and the second stages, where the capacitor transforms an impedance of the passive network to an optimal load for the first amplifier stage.

Disclosed herein are methods for amplifying a signals. The methods include receiving signals at a plurality of input nodes. The methods also include configuring a gain stage to be in a selected one of a plurality of gain settings, at least some of the gain settings resulting in different impedances presented to the signal. The methods also include adjusting the resistance presented to the signal by the gain stage for the selected gain setting, the adjusted resistance being configured to provide a targeted constant value of the impedance at the input across the plurality of gain settings. The methods also include amplifying at least a portion of the received signals. Adjusting the resistance compensates for changes to the input impedance to improve return loss and mismatch over gain modes.

An apparatus includes an amplifier and a gain control circuit. The amplifier may be configured to provide multiple gain steps. The gain control circuit may be configured to provide fast and precise changes between the multiple gain steps of the amplifier. The gain control circuit may be further configured to change an impedance of the amplifier to switch between the gain steps. The gain control circuit may be further configured to compensate for changes in frequency response related to changing the impedance. The gain control circuit may be further configured to inject a complementary charge to an input of the amplifier to correct a bias voltage deviation and a transient caused by the gain control circuit.