A power amplifier circuit for peak envelope modulation of a high frequency signal is provided. The power amplifier circuit includes a transformer which receives a first signal greater than a predetermined level of an envelope of a carrier signal to generate a transformed signal, and a transistor which operates based on the transformed signal, receives a second signal, which is generated based on the carrier signal and has a direct current component, and amplifies the second signal according to t...

An optical integrated device includes a plurality of input optical waveguides connected respectively to a plurality of input ports provided on one end face of the optical integrated device, a single output optical waveguide connected to an output port, an optical coupler for optically coupling signal lights propagated along the plural input optical waveguides to the single output optical waveguide, and a semiconductor optical amplifier gate array formed from a plurality of semiconductor optical ...

A method of controlling output power in a power amplifier having a driver stage and an output stage. The driver current is measured and the output stage biased in dependence upon the measured driver current.

A positioning and control system to selectively position and to monitor and record the position of the seat frame, back rest frame and leg rest supports of a powered wheelchair wherein the positioning and control system comprises a seat positioning mechanism including a seat tilt positioning assembly and a back rest recline positioning assembly to position the tilt of the seat frame and the recline of the back rest frame respectively, and a leg rest positioning mechanism including leg rest posit...

A RFPA (radio frequency power amplifier) circuit (150) which includes a RFPA (101), a supply voltage source (104), means (155) for applying to the RFPA a gain control bias voltage and a feedback control loop (156) for adjusting a voltage applied to the RFPA, the feedback control loop including a sampler (107) for sampling an output of the RFPA, a RF detector (109) for detecting a level of RF power sampled by the sampler, a comparator (115) for comparing an output signal from the RF detector with...

In response to a change in a circuit parameter of a converter delivering power to a load, the converter is operated in a mode in which additional power is supplied to the load by a capacitive element that is in parallel with the converter, the circuit parameter including a parameter other than input current.

A system includes a lift chair having sensors embedded therein to determine various factors such as the amount of pressure exerted in various portions of the chair, the activity level of the chair user, whether the chair is occupied and which user is currently occupying the chair, and how much assistance the chair provides the user. The information detected by the sensors can be transmitted via the Internet, for example, to a third party device, such as a doctor's personal computer, which is als...

A positioning and control system to selectively position and to monitor and record the position of the seat frame, back rest frame and leg rest supports of a powered wheelchair wherein the positioning and control system comprises a seat positioning mechanism including a seat tilt positioning assembly and a back rest recline positioning assembly to position the tilt of the seat frame and the recline of the back rest frame respectively, and a leg rest positioning mechanism including leg rest posit...

A power amplifier controller for adjusting a supply voltage to a power amplifier. The power amplifier controller adjusts the supply voltage so that distortion in an RF output signal corresponds to a predetermined limit. An amplitude error signal is generated by the power amplifier controller which represents a difference between an RF output signal and an attenuated RF output signal. The AC components of the amplitude error signal are processed to generate a deviation signal that represents the ...

A bias circuit for a smart power amplifier includes a high power mode bias circuit and a low power mode bias circuit, and operates only one of the bias circuits selectively using a switching circuit according to an input signal. Therefore, the bias circuit of high power mode and the bias circuit of the low power mode are divided and can be optimized according to characteristics of the power. Accordingly, a gain difference with respect to each power can be minimized and the low power mode can be ...