Abstract: The present invention includes a power amplifying stage having a power amplifying element having a main electrode and a control electrode, and a bias control circuit that is supplied with a bias switching voltage and an operating point adjusting voltage for adjusting the bias voltage value to the control electrode of the power amplifying element by the bias switching voltage and the operating point adjusting voltage and hence adjusting the operating point of the power amplifying element, wherein the bias control circuit adjusts the operating point of the power amplifying element by switching between supply and stop of the bias voltage to the control electrode of the power amplifying element by the bias switching voltage, and varying the bias voltage value to be supplied to the control electrode of the power amplifying element by the operating point adjusting voltage in phase.

Abstract: A transmission-and-receiving switching circuit includes a signal input-and-output end to which an antenna is connected; a transmission circuit connected to the signal input-and-output end through a first switching diode; a receiving circuit connected to the signal input-and-output end through a second switching diode; and first and second inductor elements for feeding bias voltages to the first switching diode and the second switching diode respectively. A first resonant circuit contains a first capacitor element and the first inductor element for at least series resonating between the first switching diode and ground. The series resonant frequency of the first resonant circuit is about equal to a frequency of a signal other than the transmission signal output from the transmission circuit.

Abstract: The present invention includes a power amplifying stage having a power amplifying element having a main electrode and a control electrode, and a bias control circuit that is supplied with a bias switching voltage and an operating point adjusting voltage for adjusting the bias voltage value to the control electrode of the power amplifying element by the bias switching voltage and the operating point adjusting voltage and hence adjusting the operating point of the power amplifying element, wherein the bias control circuit adjusts the operating point of the power amplifying element by switching between supply and stop of the bias voltage to the control electrode of the power amplifying element by the bias switching voltage, and varying the bias voltage value to be supplied to the control electrode of the power amplifying element by the operating point adjusting voltage in phase.

Abstract: A wireless LAN (local area network) card includes a circuit board having a plurality of connector terminals; a transmission and reception circuit formed on a surface of the circuit board; a baseband circuit formed on the surface; a non-volatile memory mounted on the surface; and a box-shaped cover for covering the transmission and reception circuit. The non-volatile memory is disposed in the vicinity of the transmission and reception circuit so that the transmission and reception circuit and the non-volatile memory are covered by the cover. The wireless LAN card requires no coating resin, and is therefore efficient in usability and cost.

Abstract: A frequency conversion circuit includes a first mixer for performing frequency conversion of a received signal having components disposed at first frequency intervals into a first intermediate frequency signal which has a frequency lower than that of the received signal and which has components disposed at predetermined frequency intervals, two second mixers for performing frequency conversion of the first intermediate frequency signal into a second intermediate frequency signal having a frequency lower than that of the first intermediate frequency signal. A first local oscillation signal changing at second frequency intervals different from the first frequency intervals is supplied to the firs mixer, and a second local oscillation signal having a frequency which is the reciprocal of an integer of the frequency of the first local oscillation signal is supplied to the second mixers.

Abstract: An output power detection circuit of a transmitter, which can accurately detect a power outputted from a power amplifier without depending on a change in ambient temperature is realized. The circuit comprises: a first diode to which a first bias direct current is applied; first load resistors through which the first bias direct current flows; a second diode to which a second bias direct current is applied; second load resistors through which the second bias direct current flows; and a differential amplifier. A first voltage generated in the first load resistor and a second voltage generated in the second load resistor are made substantially the same and are applied to the differential amplifier, a detection voltage obtained by detecting operation of the first diode is added to the first voltage, and a voltage corresponding to the power generated from a power amplifier is detected.

Abstract: A reception circuit for a cellular telephone according to the present invention shares the use of a code division multiple access system and a frequency division multiple access system, comprises: an amplifier circuit at the forefront stage; a bypass circuit connected to the amplifier circuit at the forefront in parallel therewith, having lower gain than the amplifier circuit at the forefront stage; and a common processing circuit connected to the latter stages of the amplifier circuit at the forefront and the bypass circuit, and when the level of a received signal is not higher than predetermined voltage, induces the received signal to the processing circuit through the amplifier circuit at the forefront while when the level of the received signal exceeds the predetermined voltage, the received signal is induced to the processing circuit through the bypass circuit.

Abstract: A balanced-to-unbalanced converting circuit in which balanced-to-unbalanced converters are formed by a stripline in such a manner as to include a copper foil pattern which is formed on an inner or surface printed circuit layer of a multi-layer substrate and are connected to a double balanced mixer serving as a surface-mounted component provided on a first printed circuit. In the case of this converting circuit, a part of conventional surface-mounted components are eliminated from the multi-layer substrate. Thereby, the high density packaging of other surface-mounted components can be achieved. This contributes to the miniaturization, thickness reduction, weight reduction and price reduction of an entire portable telephone. Further, the balanced-to-unbalanced converters are formed by placing the copper foil pattern on a printed circuit layer which is sandwiched between grounded conductor layers of the multi-layer substrate.