Abstract: In a resistance control circuit, each source electrode of the first and second MOSFETs is connected to VDD, respectively, the first current source is connected to a point between a drain electrode of the first MOSFET and the ground, a non-reverse input terminal of an operation amplifier is connected to a drain electrode of the first MOSFET, and an output terminal of the operation amplifier is connected to the first and second MOSFETs. A voltage applying device applies a predetermined voltage to the reverse input terminal of the operation amplifier so that the MOSFETs is operated in MOS Ohmit region.

Abstract: An analog multiplication circuit for outputting an output multiplied by an input electric current with a predetermined number can be provided with a simple structure. The circuit comprises a gate voltage control portion 1 having a first operation amplifier 13 and a first MOSFET 14 operated in a MOS Ohmic region and at least one operation portion 3 having the second operation amplifier 32, a first resistance 31, an electric current mirror circuit 34 and a second MOSFET 33 operated in a MOS Ohmic region, wherein a first input electric current I1 is supplied to the first MOSFET 14 and a second input electric current I2 is supplied to the first resistance 31 so as to output an output electric current IOUT by multiplying I1 with I2 from an output-side transistor 36 of the electric mirror circuit 34.

Abstract: A purpose of the present invention is to provide an economical frequency multiplier with a simple structure, wherein a frequency of an input signal can be multiplied with high accuracy and the frequency multiplier is widely applicable to a device in which a high accurate high frequency is required. The frequency multiplier comprises at least a differential signal generating circuit 11 for receiving a sinusoidal wave input signal and generating two signals of which a frequency is as same as that of the input signal and a phase different is 180° and a multiplier circuit 12 for multiplying two signals from the differential signal generating circuit 11 and generating a signal of which a frequency component is double of an original frequency of the input signal so as to obtain an output signal of which a frequency is multiplied in response to the input signal.

Abstract: A laser diode driver solves problems of APC (Auto Power Control) group, a LD monitor group, and an optical output waveform, which occur when reducing adjusting resistors constituted in a conventional laser diode drive.

Abstract: An apparatus for detecting an overcurrent flowing in a power element comprises a sampling resistor, a detector resistor, a reference resistor, a reference potential generator, and a comparator. The sampling resistor generates a sampling potential according to a current flowing in the power element. The detector resistor generates a reference potential. The reference resistor retains a constant resistance ratio relative to the sampling resistor. The reference potential generator alters the reference potential in accordance with a current flowing across the reference resistor. The comparator compares the sampling potential with the reference potential to thereby detect an overcurrent in the power element.