A Doherty amplifier is configured in such a way that a phase adjustment circuit adjusts either the phase of a return signal going to a first auxiliary amplification element as a result of passage of a first signal amplified by a second main amplification element through a second auxiliary amplification element as the return signal, or the phase of the return signal going to the second auxiliary amplification element as a result of reflection of the return signal by the first auxiliary amplification element, at a time of a backoff operation of the second auxiliary amplification element, in such a way that the sum of the phase of the return signal going to the first auxiliary amplification element and the phase of the return signal going to the second auxiliary amplification element is not equal to 0 degrees in the operating frequency band of the first signal.

A Doherty amplifier is configured in such a way that a phase adjustment circuit adjusts either the phase of a return signal going to a first auxiliary amplification element as a result of passage of a first signal amplified by a second main amplification element through a second auxiliary amplification element as the return signal, or the phase of the return signal going to the second auxiliary amplification element as a result of reflection of the return signal by the first auxiliary amplification element, at a time of a backoff operation of the second auxiliary amplification element, in such a way that the sum of the phase of the return signal going to the first auxiliary amplification element and the phase of the return signal going to the second auxiliary amplification element is not equal to 0 degrees in the operating frequency band of the first signal.

A filter includes an input terminal, an output terminal, a ground terminal, a first capacitor and a second capacitor that are connected in series between the input terminal and the output terminal, a capacitive element that is connected in parallel to the first capacitor and the second capacitor between the input terminal and the output terminal, and has a Q factor that is smaller than a Q factor of the first capacitor and is smaller than a Q factor of the second capacitor, and an inductor that has a first end and a second end, the first end being coupled to a node that is provided between the first capacitor and the second capacitor and that is coupled to the capacitive element through the first capacitor and the second capacitor, the second end being coupled to the ground terminal.

A termination/attenuation network applies to an input of a set-top box a MOCA channel signal having a narrow band of frequencies and included in RF signals having a wide band of frequencies received via a cable from a satellite antenna. The network includes a pair of series resistors and a parallel resistor coupled to a junction terminal between the pair of series resistors in a T-shaped configuration. A series-pass band-pass filter (L1, C2) bypasses the pair of series resistors and a parallel band stop filter (L2, C1) decouples the parallel resistor at the frequency band of the MOCA channel signal for selectively reducing attenuation at the frequency band of the MOCA channel signal.

A filter (10) includes two capacitors (C1a and C1b) that are connected in series on a path connecting an input terminal (101a) and an output terminal (102a), an inductor (L2) that is connected in parallel with a series circuit including the two capacitors (C1a and C1b), and a parallel-arm resonator (P1) that is connected between the ground and a node (N) between the two capacitors (C1a and C1b) on the path.

A filter circuit has a first resistor which is connected between an input node and an output node, a second resistor which is connected between the output node and a reference potential node, a first capacitor and a second capacitor which are connected in series between the input node and the output node, and a variable capacity part which is connected between a connection node of the first capacitor and the second capacitor and the reference potential node.

A filter (10) includes two capacitors (C1a and C1b) that are connected in series on a path connecting an input terminal (101a) and an output terminal (102a), an inductor (L2) that is connected in parallel with a series circuit including the two capacitors (C1a and C1b), and a parallel-arm resonator (P1) that is connected between the ground and a node (N) between the two capacitors (C1a and C1b) on the path.

The present invention is directed to communication systems and electrical circuits. More specifically, an embodiment of the present invention provides a termination circuit that includes a programmable gain attenuation section, a T-coil section, and a termination resistor. The characteristic resistance of the programmable gain attenuation section matches the resistance of the termination resistor. There are other embodiments as well.

A filter circuit has a first resistor which is connected between an input node and an output node, a second resistor which is connected between the output node and a reference potential node, a first capacitor and a second capacitor which are connected in series between the input node and the output node, and a variable capacity part which is connected between a connection node of the first capacitor and the second capacitor and the reference potential node.

An attenuation cell is provided for use in a switched attenuator. The attenuation cell includes an attenuation path that has an input, a first switch, a resistive network, a second switch, and an output. The resistive network provides a desired attenuation from the input to the output. The attenuation cell also includes a bypass path in parallel with the attenuation path with a bypass switch between the input and the output. The attenuation cell also has a shunt switch coupled between the resistive network and a reference node to selectively connect the resistive network to the reference node.