Bias circuits and methods for silicon-based amplifier architectures that are tolerant of supply and bias voltage variations, bias current variations, and transistor stack height, and compensate for poor output resistance characteristics. Embodiments include power amplifiers and low-noise amplifiers that utilize a cascode reference circuit to bias the final stages of a cascode amplifier under the control of a closed loop bias control circuit. The closed loop bias control circuit ensures that the current in the cascode reference circuit is approximately equal to a selected multiple of a known current value by adjusting the gate bias voltage to the final stage of the cascode amplifier. The final current through the cascode amplifier is a multiple of the current in the cascode reference circuit, based on a device scaling factor representing the relative sizes of the transistor devices in the cascode amplifier and in the cascode reference circuit.

One aspect of this disclosure is a power amplifier system that includes a control interface, a power amplifier, a passive component, and a bias circuit. The power amplifier and the passive component can be on a first die. The bias circuit can be on a second die. The control interface can operate as a serial interface or as a general purpose input/output interface. The power amplifier can be controllable based at least partly on an output signal from the control interface. The bias circuit can generate a bias signal based at least partly on an indication of the electrical property of the passive component. Other embodiments of the system are provided along with related methods and components thereof.

A low noise amplifier includes a transistor that amplifies and outputs inputted signals, a buffer that propagates outputs of the transistor to a subsequent circuit, a variable current source that supplies a bias current to the transistor, and a variable resistor connected between a gate terminal of the transistor and a terminal of the transistor to which the variable current source is connected, wherein in a case in which the inputted signals do not pass through the low noise amplifier, the buffer blocks outputs of the transistor, and settings of the variable current source and the variable resistor differ from settings in a case in which the inputted signals pass through the low noise amplifier.

An amplifier circuit is disclosed. The amplifier circuit includes an input terminal configured to receive an input signal, an output terminal configured to transmit an output signal, and a first signal path including a first amplifying circuit, where the first amplifying circuit is configured to receive the input signal and to transmit a first amplified output to the output terminal, and where the first amplified output includes first amplifier circuit harmonic noise. The amplifier circuit also includes a second signal path including a second amplifying circuit, where the second amplifying circuit receives the input signal and transmits a second amplified output to the output terminal, and where the second amplified output includes second amplifier circuit harmonic noise. The output signal includes the first and second amplified outputs, and the first amplifying circuit harmonic noise is at least partially canceled by the second amplifying circuit harmonic noise in the output signal.

An active filter reduces Electro-Magnetic Interference (EMI) created by current flowing through a power line. The active filter connects to the power line at a single node through a connection capacitor. A sense current flows through the connection capacitor when the power line current changes. This sense current is applied to a non-inverting input of an op amp to drive a power amplifier circuit through a filter capacitor. The power amplifier circuit increases the current drive of the op amp to charge a transfer capacitor that converts the power amplifier output current to a transfer voltage. The transfer capacitor is connected to the connection capacitor so that the transfer voltage is injected back into the power line through the connection capacitor as an injected voltage that compensates for the sensed current. Op amp gain is adjustable by variable resistors that connect to the inverting input of the op amp.

Reducing a sensitivity of an electromechanical sensor is presented herein. The electromechanical sensor comprises a sensitivity with respect to a variation of a mechanical-to-electrical gain of a sense element of the electromechanical sensor; and a voltage-to-voltage converter component that minimizes the sensitivity by coupling, via a defined feedback capacitance, a positive feedback voltage to a sense electrode of the sense element—the sense element electrically coupled to an input of the voltage-to-voltage converter component. In one example, the voltage-to-voltage converter component minimizes the sensitivity by maintaining, via the defined feedback capacitance, a constant charge at the sense electrode. In another example, the electromechanical sensor comprises a capacitive sense element comprising a first node comprising the sense electrode. Further, a bias voltage component can apply a bias voltage to a second node of the electromechanical sensor. In yet another example, the electromechanical sensor comprises a piezoelectric sense element.

An amplifier circuit includes a voltage-to-current conversion circuit and a current-to-voltage conversion circuit. The voltage-to-current conversion circuit generates a current signal according to an input voltage signal, and includes an operational transconductance amplifier (OTA) used to output the current signal at an output port of the OTA. The current-to-voltage conversion circuit generates an output voltage signal according to the current signal, and includes a linear amplifier (LA), wherein an input port of the LA is coupled to the output port of the OTA, and the output voltage signal is derived from an output signal at an output port of the LA.

An amplifier circuit is disclosed. The amplifier circuit includes an input terminal configured to receive an input signal, an output terminal configured to transmit an output signal, and a first signal path including a first amplifying circuit, where the first amplifying circuit is configured to receive the input signal and to transmit a first amplified output to the output terminal, and where the first amplified output includes first amplifier circuit harmonic noise. The amplifier circuit also includes a second signal path including a second amplifying circuit, where the second amplifying circuit receives the input signal and transmits a second amplified output to the output terminal, and where the second amplified output includes second amplifier circuit harmonic noise. The output signal includes the first and second amplified outputs, and the first amplifying circuit harmonic noise is at least partially canceled by the second amplifying circuit harmonic noise in the output signal.

A receiver front end amplifier 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 capacitors for each leg can be used to further improve the matching performance of the invention.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.