A tunable impedance simulator and impedance multiplier circuit and a system for configuring a second generation voltage-mode conveyor circuit (VCII) as the tunable impedance simulator and impedance multiplier are described. The tunable impedance simulator and impedance multiplier circuit includes one VCII having a positive input terminal connected to a voltage source, a negative input terminal connected to the voltage source, and an impedance terminal Z.sub.0. The impedance terminal Z.sub.0 can be either positive or negative. When the impedance terminal Z.sub.0 is positive, a positive active inductor, a positive capacitance multiplier, and a positive resistance multiplier may be implemented. When the impedance terminal Z.sub.0 is negative, a negative active inductor, a negative capacitance simulator, and a negative resistance simulator may be implemented.

Various embodiments for controlling a resonant frequency of a resonator are described. A system includes at least one resonant circuit and an active variable reactance circuit that controls a resonant frequency of the at least one resonant circuit. The active variable reactance circuit includes an electrically-controllable switching element and a switch controller sub-circuit configured to switch the electrically-controllable switching element at a frequency of a radio-frequency (RF) current or voltage passing through or across a device such that the RF current flowing from a first terminal to a second terminal is substantially sinusoidal.

A circuit and method for protecting circuit elements, vehicle having the circuit, and method for controlling the vehicle are provided. The circuit for protecting circuit elements includes a circuit element, a driving signal generator that applies a driving voltage to the circuit element and an inductor with a first terminal electrically connected to the circuit element. A circuit protector obtains information regarding the driving voltage applied to the circuit element and a differential voltage across the first terminal and a second terminal of the inductor, compares the driving voltage applied to the circuit element with a first reference voltage, compares the differential voltage with a second reference voltage, and then transmits a control signal to the driving signal generator according to the comparison results.

A circuit and method for protecting circuit elements, vehicle having the circuit, and method for controlling the vehicle are provided. The circuit for protecting circuit elements includes a circuit element, a driving signal generator that applies a driving voltage to the circuit element and an inductor with a first terminal electrically connected to the circuit element. A circuit protector obtains information regarding the driving voltage applied to the circuit element and a differential voltage across the first terminal and a second terminal of the inductor, compares the driving voltage applied to the circuit element with a first reference voltage, compares the differential voltage with a second reference voltage, and then transmits a control signal to the driving signal generator according to the comparison results.

A switched mode negative inductance circuit includes an input node responsive to a voltage signal. The circuit also includes first and second voltage sources, first and second controlled switches having first poles coupled to the first and second voltage sources, respectively and an inductor having a first electrode coupled to second poles of the first and second controlled switches and a second electrode coupled to the input node. The input node is coupled to a control electrode of the first controlled switch, and to a control electrode of the second controlled switch through a voltage inverting circuit. The disclosure also illustrates balanced negative inductance circuits and implementation approaches using NMOS transistors.

A switched mode negative inductance circuit includes an input node responsive to a voltage signal. The circuit also includes first and second voltage sources, first and second controlled switches having first poles coupled to the first and second voltage sources, respectively and an inductor having a first electrode coupled to second poles of the first and second controlled switches and a second electrode coupled to the input node. The input node is coupled to a control electrode of the first controlled switch, and to a control electrode of the second controlled switch through a voltage inverting circuit. The disclosure also illustrates balanced negative inductance circuits and implementation approaches using NMOS transistors.

A circuit for controlling a capacitor having a capacitance adjustable by biasing, including an amplifier for delivering a D.C. bias voltage, having a feedback slowed down by a resistive and capacitive cell.

A radio frequency integrated circuit includes an amplification circuit for outputting a radio frequency signal to an antenna, a balun including a first terminal, a second terminal, a third terminal, and a fourth terminal, and a variable capacitance circuit including a fifth terminal and a sixth terminal. The first terminal and the second terminal of the balun receive output signals of the amplification circuit. The third terminal and the fourth terminal of the balun are connected to the fifth terminal and the sixth terminal of the variable capacitance circuit, respectively, and the fifth terminal is connected to a radio frequency output terminal. The variable capacitance circuit includes a plurality of capacity cells that are connected in parallel between two output terminals.

A tunable grounded positive and negative active inductor simulator and impedance multiplier circuit and a method for implementing the tunable grounded positive and negative active inductor simulator and impedance multiplier circuit are described. The circuit includes one second generation voltage-mode conveyor circuit (VCII+), a voltage source configured to generate an output current, a first impedance, a second impedance and an operational transconductance amplifier OTA. The first impedance is connected between the voltage source and the positive VCII+ input terminal, Y. The second impedance is connected between the second output terminal and a ground terminal. The OTA is configured to have a transconductance gain. The circuit is configured to be tuned by a selection of values for the first and second impedances.

A digital communication station includes a coupled inductor, driver circuitry, and a digital transceiver. The coupled inductor includes (1) a first winding connected between a first digital communication node and a first power node, (2) a second winding connected between a second digital communication node and a second power node, and (3) a third winding. The driver circuitry is configured to drive the third winding to increase respective inductance values of the first and second windings, and the digital transceiver is communicatively coupled to the first digital communication node and the second digital communication node.