FET amplifier

About: FET amplifier is a research topic. Over the lifetime, 7048 publications have been published within this topic receiving 77549 citations.

Short-circuit protection and over-current modulation to maximize audio amplifier output power

Abstract: A Class D amplifier includes a tracking circuit and a regulation circuit to provide efficient, accurate protection against excessive current flow in the power FET's of the amplifier output stage. The FET currents flowing in the output stage are mirrored across tracking resistors by the tracking circuit. The resultant voltage drops are compared to reference voltages to detect over-current situations. By mirroring scaled-down versions of the output currents, power consumption in the tracking circuit is minimized. When an over-current situation is detected, the regulation circuit modulates the duty cycle of the signal input to the output stage until the FET currents fall to acceptable levels. If two over-current indications occur during a single clocking cycle of the pulse-width modulator of the amplifier, the regulation circuit shuts off the amplifier to protect against short-circuit damage.

Multi-cascode amplifier bias techniques

Abstract: Techniques for generating bias voltages for a multi-cascode amplifier In an aspect, a multi-cascode bias network is provided, each transistor in the bias network being a replica of a corresponding transistor in the multi-cascode amplifier, which enables accurate biasing of the transistors in the multi-cascode amplifier In a further aspect, a voltage supply for the multi-cascode amplifier is provided separately from a voltage supply for the replica bias network, to advantageously decouple variations in the amplifier voltage supply from the bias network voltage supply In yet another aspect, the bias voltages of transistors in the multi-cascode amplifier may be configured by adjusting the impedance of resistive voltage dividers coupled to the transistor gate biases As the gain of the amplifier depends on the bias voltages of the cascode amplifiers, the gain of the amplifier may advantageously be adjusted in this manner without introducing a variable gain element directly in the amplifier signal path

High efficiency feed-forward RF power amplifier with predistoration enchancement

Abstract: An RF power amplifier linearization architecture contains main and auxiliary path RF amplifiers. A distortion-inverting circuit (100) extracts the distortion component from the output signal of the main amplifier (A1) and combines it with a delayed sample of the RF input signal to drive an auxiliary path RF amplifier (A2), via a predistorter (293). An output quadrature hybrid (200) combines the output of the main and auxiliary path amplifiers. The cascading of the distortion-inverting circuit with the predistorter compensates for the non-linear behavior of the auxiliary path RF power amplifier (A2) thereby producing a composite signal at the output quadrature hybrid (200), in which RF carrier components from each amplifier combine constructively while distortion components cancel.

Monolithic GaAs travelling-wave amplifier

Abstract: A monolithic GaAs travelling-wave amplifier with distributed input and output lines is described, and its experimental performance in the 0.5-14 GHz range is reported.

Apparatus and method to provide power amplification

Abstract: Briefly, in accordance with an embodiment of the invention, an apparatus and method to increase efficiency of a power amplifier is provided. The apparatus may include a power amplifier, and a variable impedance matching circuit coupled to the power amplifier to improve the transmitter efficiency over a range of output power. The variable impedance matching circuit may be adapted to match the output impedance of the power amplifier. The method may include varying the impedance of a circuit coupled to the output of a power amplifier during operation of the power amplifier to match the output impedance of the power amplifier.