A current control circuit controls a base current of a first transistor included in a bias circuit outputting a bias current to a power amplifier based on a base-collector voltage of the first transistor. The current control circuit includes a first circuit that outputs a signal associated with the base-collector voltage of the first transistor, and a second circuit that, based on the signal, provides electrical continuity between a base of the first transistor and a reference potential.

A bias circuit includes first to fourth transistors and a phase compensation circuit. In the first transistor, a reference current or voltage is supplied to a first terminal, and the first terminal and a second terminal are connected. In the second transistor, a first terminal is connected to the first transistor, and a third terminal is grounded. In the third transistor, a power supply voltage is supplied to a first terminal, a second terminal is connected to the first transistor, and a bias current or voltage is supplied from a third terminal to an amplifier transistor. In the fourth transistor, a first terminal is connected to the third transistor, a second terminal is connected to the second transistor, and a third terminal is grounded. The phase compensation circuit is provided in a path extending from the fourth transistor to the third transistor through the second and first transistors.

The present disclosure relates to an electronic device comprising a first capacitor and a quartz crystal coupled in series between a first node and a second node; an inverter coupled between the first and second nodes; a first variable capacitor coupled between the first node and a third node; and a second variable capacitor coupled between the second node and the third node.

A radio frequency module includes: a module board that includes a first principal surface and a second principal surface on opposite sides of the module board; a power amplifier; and a first circuit component. The power amplifier includes: a first amplifying circuit element; a second amplifying circuit element; and an output transformer that includes a primary coil and a secondary coil. An end of the primary coil is connected to an output terminal of the first amplifying circuit element. Another end of the primary coil is connected to an output terminal of the second amplifying circuit element. An end of the secondary coil is connected to an output terminal of the power amplifier. The first amplifying circuit element and the second amplifying circuit element are disposed on the first principal surface. The first circuit component is disposed on the second principal surface.

A dc coupled amplifier includes a pre-driver, and amplifier and a bias control circuit. The pre-driver is configured to receive one or more input signals and amplify the one or more input signals to create one or more pre-amplified signals. The amplifier has cascode configured transistors configured to receive and amplify the one or more pre-amplified signals to create one or more amplified signals, the amplifier further having an output driver termination element. The bias control circuit is connected between the pre-driver and the amplifier, the bias control circuit receiving at least one bias current from the output driver termination element of the amplifier, wherein the pre-driver, the amplifier and the bias control circuit are all formed on a same die.

A bias circuit according to an example embodiment includes a first power source configured to generate a first gate voltage that puts an amplifying transistor in an on state; a voltage generating circuit configured to generate a second gate voltage by use of the first gate voltage input from the first power source, the second gate voltage putting the amplifying transistor in an off state; a first switching circuit configured to switch between the first gate voltage input to a first input terminal and the second gate voltage input to a second input terminal and to output the first gate voltage or the second gate voltage, based on a changeover signal related to on/off control of the amplifying transistor; and a voltage output terminal configured to output the gate voltage output from the first switching circuit to the amplifying transistor.

Apparatus and methods for providing hot-switching immunity for radio frequency switching circuits are disclosed. A radio frequency switching circuit may include both a mechanical switch and a solid-state switch. The mechanical switch may be configurable to couple an output path of a power amplifier to a subsequent component in its transmission path when in a first mechanical switch state and to decouple the output path of the power amplifier from the subsequent component when in a second mechanical switch state. The solid-state switch may be configurable to operatively decouple the mechanical switch from a radio frequency power source when in a first solid-state switch state but not when in a second solid-state switch state. The solid-state switch may be in the first solid-state switch state during transitions of the mechanical switch between the first and second mechanical switch states.

A radio-frequency module includes a module substrate, a power amplifier, and a control circuit configured to control the power amplifier. The control circuit includes a temperature sensor. The power amplifier and the control circuit are stacked one on top of another on a principal surface of the module substrate.

The present invention discloses a bias compensation circuit. The bias compensation circuit includes a detecting circuit, including a diode-connected transistor circuit, with a first end for receiving a first current, and a second end coupled to a first reference voltage end; and a first diode circuit, with a first end for receiving a second current, and a second end coupled to the first reference voltage end; wherein the detecting circuit provides a first voltage level according to the diode-connected transistor circuit, and provides a second voltage level according to the first diode circuit; a voltage-current converting circuit, coupled to the detecting circuit, for generating a first reference current according to the first voltage level and the second voltage level; and a bias circuit, coupled to the voltage-current converting circuit, for receiving the first reference current, to provide a bias voltage level according to the first reference current.

A radio-frequency circuit is provided that includes a power amplifier, a control circuit, an on-off switch, a connection terminal, and a mount board. The power amplifier supports an APT system and an ET system. The control circuit controls the power amplifier by using the APT system and the ET system. The on-off switch is connected in series to a capacitive element connected between a path and the ground. The connection terminal is connected to the capacitive element. Moreover, the control circuit overlies the connection terminal in plan view in the thickness direction of the mount board.