An amplifier switchable between a dual-channel amplifier and a BTL amplifier includes first and second amplifying circuits having a non-inverting input, an inverting input and an output, a first input terminal receiving a first input signal and applying it to the non-inverting input of the first amplifying circuit, a second input terminal receiving a second input signal, a first switch selectively applying a signal to the non-inverting input of the first or second amplifying circuit, a second switch controlling the application of an output from the first amplifying circuit to the inverting input of the second amplifying circuit, a controlling circuit controlling the first and second switches, first through third loads and a third switch controlling the application of an output from the first and second amplifying circuits to the first and second loads, respectively, or to the respective ends of the third load.

A multichannel parallel IC amplifier includes a plurality of amplifier circuits formed on an IC substrate. Each amplifier circuit is coupled to respective inputs via a pair of capacitors. The capacitors are configured so as to substantially equalize like sense and unlike sense coupling between adjacent channels, leading to cancellation of crosstalk signals.

An RF power amplifier network with a redundant power supply comprising a plurality of RF power amplifiers. Each RF power amplifier includes a power supply unit and an amplifier load. The power supply unit is adapted for receiving a primary input voltage Vin and producing a secondary output voltage Vout, and the power supply unit is further adapted for generating a power supply fail signal upon failure of the power supply unit. The network further includes a supply bus to which is connected each power supply unit of each RF power amplifier, and each amplifier load of each RF power amplifier. A switch associated with each of the power supply units is responsive to the fail signal for disconnecting the power supply unit from the bus in the event of failure of the power supply unit. A second switch is associated with each of the RF power amplifiers for disconnecting an amplifier load from the bus if the current drawn by the amplifier load exceeds a predetermined maximum threshold value or falls below a predetermined minimum threshold value.

An amplifier operating from a plurality of power sources in which current flows through ground loops between power sources supplying operating power to different stages are eliminated. The output of a voltage amplifying stage is applied to a high input impedance buffer input circuit of a following buffer amplifying stage. The output of the power amplifying stage is voltage divided and applied to a feedback buffer circuit, the output of which is applied to an inverting input terminal of the voltage amplifying stage. Accordingly, due to the high impedance of the input of the power amplifying stage and of the feedback buffer, substantially no currents flow between the stages, hence eliminating ground current flows.

A microwave heating apparatus comprises a solid state oscillating circuit, a pre-amplifier module for amplifying the output of the oscillating circuit, a plurality of amplifier modules for amplifying the output of the pre-amplifier module, a first power supply source for energizing the solid state oscillating circuit and a second power supply source for energizing all of the amplifier modules. Such an apparatus further comprises a delay circuit for activating the first power supply source after the second power supply source has been activated and the amplifier modules have been in a stable state.