Abstract: The present invention provides a PLL circuit containing a loop gain circuit capable of suppressing loop gain variation. This PLL circuit includes a counter that is driven by a voltage controlled oscillator within the PLL circuit, an accumulator (ACL) that accumulates the output of the counter, and a comparison operation circuit block that compares the count value of the ACL and the design value pre-stored in a register, and the loop gain of the PLL circuit is detected taking advantage of the fact that the ACL count value is inversely proportional to the loop gain. Based on the detection result, the loop gain is calibrated by correcting the loop gain with a charge pump current, etc. This allows the PLL circuit to maintain stable loop characteristics that will not affect the characteristics variation of each element constituting the PLL.

Abstract: A communication semiconductor integrated circuit has an oscillator circuit forming part of a transmission PLL circuit fabricated on a single semiconductor chip together with an oscillator circuit forming part of a reception PLL circuit and an oscillator circuit for an intermediate frequency. The oscillator circuit forming part of the transmission PLL circuit is configured to be operable in a plurality of bands. A circuit for measuring the oscillating frequency of the oscillator circuit forming part of the transmission PLL circuit is also used for measuring the oscillating frequency of the oscillator circuit forming part of the reception PLL circuit or for measuring the oscillating frequency of the oscillator circuit for the intermediate frequency.

Abstract: A transmitter that can reduce noise without using an SAW filter whose IC integration is hard, and copes with two modulation formats of constant envelope modulation and non-constant envelope modulation, and a downsized and low-cost wireless communication apparatus that uses the transmitter are provided. The transmitter includes a quadrature modulator that modulates an input signal by quadrature modulation, a first amplifier that amplifies a modulation signal outputted by the quadrature modulator, and a second amplifier that amplifies an output signal of the first amplifier. The first amplifier operates as a limiter when the modulation format is the constant envelope modulation, and performs linear operation when the modulation format is the non-constant envelope modulation.

Abstract: Into an internal circuit to operate in a high-frequency band, there is incorporated a protective circuit of a multistage connection which is constructed to include a plurality of diode-connected transistors having a low parasitic capacity and free from a malfunction even when an input signal higher than the power supply voltage is applied. Into an internal circuit to operate in a low-frequency band, there is incorporated a protective circuit which is constructed to include one diode-connected transistor. The protective circuits include two lines of protective circuit, in which the directions of electric currents are so reversed as to protect the internal circuits against positive/negative static electricities.

Abstract: An input/output pin for test corresponding to a test circuit of the digital section is used in common as the input/output pin for normal operation of the analog section. The selection switches are respectively provided between the relevant analog pin and analog circuit and on a signal line up to the test circuit of the digital section from the relevant analog pin and the switches are provided at both end portions of the signal line between the test circuit of digital section and the input/output pin for common use in order to fix the voltage of the signal line to the predetermined voltage such as the ground voltage during the normal operation.

Abstract: A communication semiconductor integrated circuit has an oscillator circuit forming part of a transmission PLL circuit fabricated on a single semiconductor chip together with an oscillator circuit forming part of a reception PLL circuit and an oscillator circuit for an intermediate frequency. The oscillator circuit forming part of the transmission PLL circuit is configured to be operable in a plurality of bands. A circuit for measuring the oscillating frequency of the oscillator circuit forming part of the transmission PLL circuit is also used for measuring the oscillating frequency of the oscillator circuit forming part of the reception PLL circuit or for measuring the oscillating frequency of the oscillator circuit for the intermediate frequency.

Abstract: In a communication semiconductor integrated circuit device, an oscillator (VCO 10) of a PLL circuit can operate in a plurality of frequency bands. With a control voltage (Vc) of the oscillator fixed to a predetermined value (VDC), an oscillation frequency of the oscillator is measured for each band to be stored in a storage (18). When the PLL operates, a setting value to specify a band is compared with the measured frequency values stored in the storage. As a result of the comparison, a band to be actually used by the oscillator is determined.

Abstract: A transceiver suitable for larger scale of integration employs direct conversion reception for reducing the number of filters. Also, the number of VCOs is reduced by utilizing dividers to supply a receiver and a transmitter with locally oscillated signals at an RF band. Dividers each having a fixed division ratio are used for generating locally oscillated signals for the receiver, while a divider having a switchable division ratio are used for generating the locally oscillated signal for the transmitter. In addition, a variable gain amplifier for baseband signal is provided with a DC offset voltage detector and a DC offset canceling circuit for supporting high speed data communications to accomplish fast cancellation of a DC offset by eliminating intervention of a filter within a feedback loop for offset cancellation.

Abstract: An image input system comprises a solid state image pickup device and a preprocessor (3) for performing correlated double sampling amplification on an output signal of the solid state image pickup device and outputting a video signal. The preprocessor comprises: a correlated double sampling amplifier (30) for outputting signal information corresponding to a difference voltage between the black level in a feedthrough period of the solid state image pickup device and a signal level in a charge signal output period; and offset cancelling means (38) for applying an offset cancelling voltage for cancelling an offset voltage corresponding to the difference voltage between the black level and the signal level in a state where the solid state image pickup device is optically interrupted to the input terminal of the correlated double sampling amplifier. The correlated double sampling amplifier cancels out the offset voltage and the offset cancelling voltage as signal components of polarities opposite to each other.

Abstract: An image input system includes a solid state image pickup device and a preprocessor for performing correlated double sampling amplification on an output of the image pickup device and outputting a video signal. The preprocessor has a correlated double sampling amplifier for outputting signal information corresponding to a difference voltage between the black level in a feedthrough period of the image pickup device and a signal level in a charge signal output period; and an offset cancelling circuit for cancelling an offset voltage corresponding to the difference voltage in a state where the image pickup device is optically interrupted to the input terminal of the correlated double sampling amplifier. The correlated double sampling amplifier cancels out the offset voltage and the offset cancelling voltage as signal components of polarities opposite to each other, so that circuits following the correlated double sampling amplifier are not influenced by the offset voltage.

Abstract: A wireless communication system, which is provided with a PLL circuit having a plurality of oscillators and is capable of processing two or more transmit and receive signal different in frequency band from one another according to the switching between the oscillators, has a reset means which resets a voltage applied to each of filter capacitors lying within the PLL circuit to a predetermined voltage when the switching between the oscillators is performed.

Abstract: A transceiver suitable for larger scale of integration employs direct conversion reception for reducing the number of filters. Also, the number of VCOs is reduced by utilizing dividers to supply a receiver and a transmitter with locally oscillated signals at an RF band. Dividers each having a fixed division ratio are used for generating locally oscillated signals for the receiver, while a divider having a switchable division ratio are used for generating the locally oscillated signal for the transmitter. In addition, a variable gain amplifier for baseband signal is provided with a DC offset voltage detector and a DC offset canceling circuit for supporting high speed data communications to accomplish fast cancellation of a DC offset by eliminating intervention of a filter within a feedback loop for offset cancellation.

Abstract: A transceiver suitable for larger scale of integration employs direct conversion reception for reducing the number of filters. Also, the number of VCOs is reduced by utilizing dividers to supply a receiver and a transmitter with locally oscillated signals at an RF band. Dividers each having a fixed division ratio are used for generating locally oscillated signals for the receiver, while a divider having a switchable division ratio are used for generating the locally oscillated signal for the transmitter. In addition, a variable gain amplifier for baseband signal is provided with a DC offset voltage detector and a DC offset canceling circuit for supporting high speed data communications to accomplish fast cancellation of a DC offset by eliminating intervention of a filter within a feedback loop for offset cancellation.

Abstract: An input/output pin for test corresponding to a test circuit of the digital section is used in common as the input/output pin for usual operation of the analog section, the selection switches are respectively provided between the relevant analog pin and analog circuit and on a signal line up to the test circuit of the digital section from the relevant analog pin and the switches are provided at both end portions of the signal line between the test circuit of digital section and the input/output pin for common use in order to fix the voltage of the signal line to the predetermined voltage such as the ground voltage during the usual operation.

Abstract: A wireless communication system, which is provided with a PLL circuit having a plurality of oscillators and is capable of processing two or more transmit and receive signal different in frequency band from one another according to the switching between the oscillators, has a reset means which resets a voltage applied to each of filter capacitors lying within the PLL circuit to a predetermined voltage when the switching between the oscillators is performed.

Abstract: Into an internal circuit to operate in a high-frequency band, there is incorporated a protective circuit of a multistage connection which is constructed to include a plurality of diode-connected transistors having a low parasitic capacity and free from a malfunction even when an input signal higher than the power supply voltage is applied. Into an internal circuit to operate in a low-frequency band, there is incorporated a protective circuit which is constructed to include one diode-connected transistor. The protective circuits include two lines of protective circuit, in which the directions of electric currents are so reversed as to protect the internal circuits against positive/negative static electricities.

Abstract: A communication semiconductor integrated circuit has an oscillator circuit forming part of a transmission PLL circuit fabricated on a single semiconductor chip together with an oscillator circuit forming part of a reception PLL circuit and an oscillator circuit for an intermediate frequency. The oscillator circuit for the transmission PLL circuit is configured to be operable in a plurality of bands. The communication semiconductor integrated circuit also comprises a circuit for measuring the oscillating frequency of the oscillator circuit for the transmission PLL circuit, and a storage circuit for storing the result of measurement made by the measuring circuit. A band to be used by the oscillator circuit for the transmission PLL circuit is determined based on values for setting the oscillating frequencies of the oscillator circuit forming part of the reception PLL circuit and the intermediate frequency oscillator circuit, and the result of measurement stored in the storage circuit.

Abstract: A communication semiconductor integrated circuit has an oscillator circuit forming part of a transmission PLL circuit fabricated on a single semiconductor chip together with an oscillator circuit forming part of a reception PLL circuit and an oscillator circuit for an intermediate frequency. The oscillator circuit forming part of the transmission PLL circuit is configured to be operable in a plurality of bands. A circuit for measuring the oscillating frequency of the oscillator circuit forming part of the transmission PLL circuit is also used for measuring the oscillating frequency of the oscillator circuit forming part of the reception PLL circuit or for measuring the oscillating frequency of the oscillator circuit for the intermediate frequency.

Abstract: Into an internal circuit to operate in a high-frequency band, there is incorporated a protective circuit of a multistage connection which is constructed to include a plurality of diode-connected transistors having a low parasitic capacity and free from a malfunction even when an input signal higher than the power supply voltage is applied. Into an internal circuit to operate in a low-frequency band, there is incorporated a protective circuit which is constructed to include one diode-connected transistor. The protective circuits include two lines of protective circuit, in which the directions of electric currents are so reversed as to protect the internal circuits against positive/negative static electricities.

Abstract: A semiconductor integrated circuit device for communication is provided with a PLL circuit or the like formed therein, the PLL circuit which is capable of realizing the compensation of fluctuation due to temperature change, the inhibition of increase in the chip area and the ensurement of the performance margin, and which controls a VCO having multiple oscillation frequency bands. In the case where automatic calibration is performed by switching a switch to a side of a DC voltage source in the PLL circuit using a VCO having multiple oscillation bands, a tuning voltage (Vtune) of an RFVCO is fixed to a voltage value of a DC voltage source. However, since a temperature characteristic of canceling a VCO oscillation frequency is given to the DC voltage source, it is possible to minimize the influence on the band selection when a calibration table comes to no optimum one.