Abstract: A frequency converter configured to convert a first current signal having a first frequency into a second current signal having a second frequency different from the first frequency is disclosed, which comprises an adder configured to add the first current signal and a predetermined reference current signal to output a third current signal corresponding to the sum of the first current signal and the reference current signal, and a switching circuit configured to pass only that portion of the third current signal which is larger in magnitude than a threshold current to output the second current signal.

Abstract: An object of the present invention is to provide an optical receiving circuit that it is possible to even a gain during a broad frequency band. The optical receiving circuit according to the present invention comprises an amplifier for feeding back negatively and amplifying an input signal, and a reflection coefficient setting circuit for setting an input reflection coefficient of the amplifier. For example, the reflection coefficient setting circuit has a resister Rin. One end of the resistor Rin is connected to an input terminal of the amplifier, and the other end of the resistor Rin is supplied with a voltage Vin substantially equal to a direct-current component of an input signal IN. The resistance of the resistor Rin is set so that the input reflection efficient becomes about less than about 0.3. Therefore, a peaking does not occur even at a resonance point, and it is possible to even a gain during a broad frequency band.

Abstract: An amplifier circuit comprises a differential amplifier configured by a differential pair of transistors, a common emitter amplifier connected in parallel to the differential amplifier and configured by a pair of common-emitter configuration transistors, input and output terminals which are common to the differential amplifier and the common emitter amplifier, and a bias controller connected to the differential amplifier and the common emitter amplifier and configured to control a bias of at least one of the differential amplifier and the common emitter amplifier.

Abstract: There is disclosed a frequency synthesizer having an HF synthesizer for generating a first reference frequency signal having a variable frequency in a high-frequency band as a unit synthesizer, an LF synthesizer for generating a second reference frequency signal in a low-frequency band as another unit synthesizer, and an arithmetic circuit including a mixer for receiving the first and second reference frequency signals, a divider for receiving the second reference frequency signal, a mixer for receiving the first reference frequency signal and an output signal from the divider, a divider for receiving an output signal from the mixer, a divider for receiving an output signal from the mixer and capable of switching a division ratio, and a switch for switching and outputting output signals from the dividers, wherein an output signal of the switch is outputted as a first local signal, and an output signal from the divider is outputted as a second local signal.

Abstract: An output circuit device is made up of a pair of output-stage transistors, a current source, and a pair of bypass transistors. The output-stage transistors have bases for receiving differential input signals, collectors connected to a load, and emitters connected to each other. The output-stage transistors amplify the differential input signals. The current source is connected to the emitters of the differential transistors. The bypass transistors lead a transient current, which is generated at the bases as a result of the switching between the output-stage transistors, to the collectors, thereby canceling noise components generated at the collectors.

Abstract: An input circuit includes a pair of common-base circuits having respective transistors including respective bases to which differential signals transmitted through a transmission line are input and constant current sources connected to the emitters of the transistors, and a level shift circuit for inputting, to the emitters of the common-base circuits, differential signals with anti-phase relation to the differential signals input to the bases of the common-base circuits. This input circuit has lower power consumption and can be used to match impedance.

Abstract: An output circuit comprising a pair of input-stage transistors supplied with an input signal, a pair of output-stage differential transistors constructing an output-stage differential circuit, a pair of wiring lines having first ends connected to the input-stage transistors, respectively, and second ends connected to the bases of the output-stage differential transistors and connecting the input-stage transistors and the output-stage transistors, respectively, a pair of input-stage constant current sources connected to the bases of the output-stage differential transistors, respectively, at the second terminals, and an output-stage constant current source connected to the output-stage differential transistors.

Abstract: An apparatus for automatically measuring dust concentration in flue gas includes (a) a sampling unit for sampling dust in flue gas; (b) a measuring unit for measuring a gas flow of the flue gas; and (c) a feeding and weighing unit for feeding and weighing a filter paper for filtering the sampled gas, the feeding and weighing unit including (i) a filter paper cassette for storing the filter paper, (ii) a filter paper stocker for storing a plurality of the filter paper cassettes, (iii) a cassette pusher unit for pushing a filter paper cassette out of the filter paper stocker, (iv) a filter paper ascending unit for raising the filter paper, (v) a filter paper drier for drying the filter paper, (vi) a filter paper transfer arm for transferring the filter paper between the filter paper cassette, the filter paper ascending unit and the filter paper drier, (vii) a vibration-free balance for balancing the filter paper, and (viii) a hot air generation unit.