The floating immittance emulator is presented in four embodiments in which four new topologies for emulating floating immittance functions are detailed. Each circuit uses three current-feedback operational-amplifiers (CFOAs) and three passive elements. The present topologies can emulate lossless and lossy floating inductances; capacitance, resistance, and inductance multipliers; and frequency-dependent positive and negative resistances.

A pseudo resistance circuit includes a first gate voltage adjustment circuit that adjusts respective currents of first and second current sources and also adjusts a gate voltage of a second field effect transistor to equalize or substantially equalize a drain voltage of the second field effect transistor and a voltage of a first end portion of a reference resistance element and controls a drain voltage of a first field effect transistor and the drain voltage of the second field effect transistor to maintain a constant or substantially constant relationship with each other; and a second gate voltage adjustment circuit that adjusts a gate voltage of the first field effect transistor to control the gate voltage of the second field effect transistor and the gate voltage of the first field effect transistor to maintain a constant or substantially constant relationship with each other.

A controller for an electronically controlled resistor, comprising a controllable current generator that outputs an output current; an amplifier receiving an input voltage proportional to the output current, and outputting an amplified input voltage to a first input of an adder; a voltage divider connected between a high-potential terminal and a low-potential terminal of the electronically controlled resistor; a buffer stage receiving an output of an external sense resistor, and outputting a buffered voltage to a controllable current generator to control the output current and to a second input of the adder, wherein the adder outputs a summed voltage; and an operational amplifier receiving the divided voltage and the summed voltage and outputting a control voltage to an external active element, wherein the active element and the sense resistor are connected in series between the high-potential terminal and the low-potential terminal of the electronically controlled resistor.

Two defense mechanisms, a hardware-based and software-based solution, are provided to protect a device during charging. The defenses randomly perturb the current drawn during charging thereby masking the unique patterns of the user's activities. It is shown that the two defenses force each one of the attacks to perform no better than random guessing, thus acting as effective defense mechanisms against all such types of attacks.

A resistive attenuator and a method for improving linearity of the resistive attenuator are provided. The resistive attenuator includes a first transistor, an attenuation circuit and a compensation circuit, wherein both the first transistor and the attenuation circuit are coupled between an input terminal and an output terminal of the resistive attenuator, and the compensation circuit is coupled to the first transistor. The first transistor is configured to provide a first signal path between the input terminal and the output terminal. The attenuation circuit is configured to provide a second signal path between the input terminal and the output terminal, wherein signal attenuation of the second signal path is greater than signal attenuation of the first signal path. The compensation circuit is configured to compensate nonlinear distortion caused by the first transistor.