Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed for particular gain modes to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores when switching gain modes to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a high gain amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity (e.g., for lower gain modes). The disclosed signal amplifiers can also have switchable reference biases to provide targeted bias current matching. The disclosed signal amplifiers can also include degeneration switching blocks for individual amplifier cores to improve signal linearity.

Methods and systems for a configurable low-noise amplifier with programmable band-selection filters may comprise a receiver with a low-noise amplifier (LNA) with first and second input terminals and differential output terminals; a low pass filter operably coupled to the LNA; a high pass filter operably coupled to the second input terminal of the LNA; and a signal source input coupled to the low pass filter and the high pass filter. The LNA may be operable to receive signals in a pass band of the high pass filter and a pass band of the low pass filter. The receiver may be operable to amplify input signals in the pass band of a first filter but not signals in the pass band of the second filter by operably coupling the second to ground.

Methods and systems for a configurable low-noise amplifier with programmable band-selection filters may comprise a receiver with a low-noise amplifier (LNA) with first and second input terminals and differential output terminals; a low pass filter operably coupled to the LNA; a high pass filter operably coupled to the second input terminal of the LNA; and a signal source input coupled to the low pass filter and the high pass filter. The LNA may be operable to receive signals in a pass band of the high pass filter and a pass band of the low pass filter. The receiver may be operable to amplify input signals in the pass band of a first filter but not signals in the pass band of the second filter by operably coupling the second to ground.

A variable gain amplifier having stabilized frequency response for widened gain control range. A resistor-capacitor compensation network is provided between two differential current input ports and corresponding emitter nodes of cross-coupled four transistors in the variable gain amplifier to desensitize the gain control voltages to the system noise and provide compensation to the VGA frequency response when the differential gain control voltage varies the gain setting, yielding a substantially stabilized frequency response over a 3 dB bandwidth ranging from 1 GHz to 60 GHz with a widened gain control range up to 12 dB without increasing power consumption.

A programmable amplifier includes an amplifier, an input capacitor, a feedback circuit, and a high-pass filter circuit. The amplifier has an input coupled to the input capacitor for receiving an input signal. The feedback circuit includes multiple feedback capacitors of differing capacitance values that are each selectively coupled between the output of the amplifier and the input of the amplifier using multiple first switches. The high-pass filter circuit includes multiple switched capacitors of differing capacitance values that are each selectively coupled between the amplifier output and a ground node using multiple second switches. The first switches are configured to be selectively switched on for activating at least one feedback capacitor to adjust a gain of the amplifier, while the second switches are configured to be selectively switched at a first and second phase of a clock signal to adjust a high-pass cutoff frequency of the amplifier independently of how the gain is adjusted.

The present disclosure describes systems and devices for gain slope equalization in a radio frequency (RF) amplifier. The RF amplifier may include an input stage for receiving an RF signal. In conjunction with the input stage, the RF amplifier may incorporate an amplification stage to amplify the RF signal. Coupled with the amplification stage may be a transformer including a first winding to receive the amplified RF signal, a second winding providing an RF output signal, and a resonator including a third winding that is coupled to the first and second windings. The resonator may be coupled to a circuit network which may be tuned to affect the resonance frequency and the gain slope of the RF output signal.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

One aspect of the present disclosure relates to a method for operating an amplifier, the amplifier including a variable resistor coupled between a source of a first input transistor and a source of a second input transistors, and a variable capacitor coupled between the source of the first input transistor and the source of the second input transistor. The method includes adjusting a resistance of the variable resistor to adjust a low-frequency gain of the amplifier, and adjusting a capacitance of the variable capacitor in an opposite direction as the adjustment to the resistance of the variable resistor.

Embodiments of the disclosure relate to a frequency selective low noise amplifier (LNA) circuit, which includes a transconductive LNA(s). In one aspect, filter circuitry is provided in a degeneration path of a transconductive LNA(s) to pass in-band frequencies and reject out-of-band frequencies by generating low impedance and high impedance at the in-band frequencies and the out-of-band frequencies, respectively. However, having the filter circuitry in the degeneration path may cause instability in the transconductive LNA. As such, a feedback path is coupled between an input node of the transconductive LNA(s) and the degeneration path to provide a feedback to improve stability of the transconductive LNA(s). In addition, the feedback can help improve impedance match in the frequency selective LNA circuit. As a result, the transconductive LNA(s) is able to achieve improved noise figure (NF) (e.g., below 1.5 dB), return loss, linearity, and stability, without compromising LNA gain.