4 results about "Tuned amplifier" patented technology

An optically controlled, multi-transmitter magnetic resonance imaging system for multi-nuclear, high field applications is disclosed. In one embodiment, the MRI system may include a dual-tuned radio-frequency (RF), on-coil power amplifier for amplifying RF power signals at two or more frequencies for the multi-nuclear excitations for use in a dual-tuned coil MRI device or a nested coil MRI device. In one particular implementation, the dual-tuned amplifier of the MRI system may receive optical carrier signals through the broadband optical interface to control the on-coil amplifiers. A variable effective inductor circuit for use in tuning the dual-tuned amplifier is also disclosed. The variable effective inductor circuit includes a gallium nitride (eGaN) field effect transistor (FET) device connected to an inductor. The inductance of the variable effective inductor circuit can be adjusted by modulating a drain-source voltage of the eGaN FET device controlled based on a pulse duration of an optical carrier signal.

A temperature controlled phase compensation circuit may include a varactor coupled between a radio frequency (RF) transmission line and a node. A temperature controlled phase compensation circuit may include a resistance coupled between a voltage supply and the node, the voltage supply configured to supply a supply voltage. A temperature controlled phase compensation circuit may include a temperature controlled current source coupled to the node and configured to produce a capacitor voltage between the varactor and the resistance, wherein a capacitor voltage produced at the node and applied to the varactor is inversely related to temperature.

An electronic circuit including an amplifier, a first variable capacitance and a second variable capacitance. The amplifier receives an input signal across an inverting input terminal of the amplifier and a non-inverting input terminal of the amplifier. The first variable capacitance is electrically directly connected to the output terminal of the amplifier and the inverting input terminal of the amplifier. The second variable capacitance is electrically directly connected to the output terminal of the amplifier and the non-inverting input terminal of the amplifier.

The invention relates to a dynamically tunable amplifier. An electronic circuit includes an amplifier, a first variable capacitor and a second variable capacitor. The amplifier receives an input signal across an inverting input terminal of the amplifier and a non-inverting input terminal of the amplifier. The first variable capacitance is directly electrically connected to the output terminal of the amplifier and the inverting input terminal of the amplifier. The second variable capacitance is directly electrically connected to the output terminal of the amplifier and the non-inverting input terminal of the amplifier.