Infrared ray receiving circuit

Claim 2

An infrared ray receiving circuit, comprising: a band pass filter comprising first and second variable trans-conductance amplifiers, said band pass filter being supplied with an input PPM signal; a detector comprising a differential switch, said detector being supplied with an output signal of said band pass filter; and a wave-form shaping circuit comprising a hysteresis comparator, said wave-form shaping circuit being supplied with an output signal of said detector; wherein said first and second variable trans-conductance amplifiers of said band pass filter are controlled by first and second output signals of first and second output terminals of a current mirror circuit; and said hysteresis comparator of said wave-form shaping circuit is controlled by a third output signal of a third output terminal of said current mirror circuit, whereby a hysteresis width of said hysteresis comparator is adjusted by said third output signal of said current mirror circuit.

Claim 3

An infrared ray receiving circuit, according to claim 1, wherein: said current mirror circuit is provided with an input terminal connected through a variable resistance to a power supply, said first to third output signals of said current mirror circuit being adjusted in current value by said variable resistance.

Claim 4

An infrared ray receiving circuit, according to claim 1, wherein each of said first and second variable trans-conductance amplifiers of said band pass filter comprises: first to fourth NPN transistors, first and second PNP transistors, first and second diodes, first and second resistances, and first and second current supplies; wherein said first NPN transistor is connected at a base to a non-reversed input terminal, at a collector to a first nodal point, and an emitter to a first terminal of said first resistance; said second NPN transistor is connected at a reversed input terminal, at a collector to a second nodal point, and at an emitter to a first terminal of said second resistance; said third NPN transistor is connected at a base to said second nodal point, at a collector to a third nodal point, and at an emitter to a fourth nodal point; said fourth NPN transistor is connected at a base to said first nodal point, at a collector to a positive terminal of a power supply, and at an emitter to said fourth nodal point; said first PNP transistor is connected at a base to a fifth nodal point which is connected to said third nodal point, at a collector to said third nodal point, and at an emitter to said positive terminal of said power supply; said second PNP transistor is connected at a base to said fourth nodal point, at a collector to an output terminal of said variable trans-conductance amplifier, and at an emitter to said positive terminal of said power supply; said first and second resistances are connected in common at each terminal to either one of said first and second output terminals of said current mirror circuit; said first diode is connected ar a cathode to said first nodal point and at an anode to said positive terminal of said power supply; said second diode is connected at a cathode to said second nodal point and at an anode to said positive terminal of said power supply; said first current supply is connected between said fourth point and ground; and said second current supply is connected between said output terminal of said variable trans-conductance amplifier and ground.

Claim 5

An infrared ray receiving circuit, comprising: a band pass filter comprising first and second variable trans-conductance amplifiers, said band pass filter being supplied with an input PPM signal; a detector comprising a differential switch, said detector being supplied with an output signal of said band pass filter; and a wave-form shaping circuit comprising a hysteresis comparator, said wave-form shaping circuit being supplied with an output signal of said detector; wherein said first and second variable trans-conductance amplifiers of said band pass filter are controlled by first and second output signals of first and second output terminals of a current mirror circuit; and said detector is controlled by a third output signal of third output terminal of said current mirror circuit, whereby a level of an output signal of said detector is adjusted by said third output signal of said current mirror circuit.

Claim 6

An infrared ray receiving circuit, comprising: a band pass filter comprising first and second variable trans-conductance amplifiers, said band pass filter being supplied with an input PPM signal; a detector comprising a differential switch, said detector being supplied with an output signal of said band pass filter; and a wave-form shaping circuit comprising a hysteresis comparator, said wave-form shaping circuit being supplied with an output signal of said detector; wherein said first and second variable trans-conductance amplifiers of said band pass filter are controlled by first and second output signals of first and second output terminals of a current mirror circuit; and said detector is controlled by a third output signal of third output terminal of said current mirror circuit, whereby a level of an output signal of said detector is adjusted by said third output signal of said current mirror circuit.

Claim 7

An infrared ray receiving circuit, according to claim 4, wherein: said current mirror circuit is provided with an input terminal connected through a variable resistance to a power supply, said first to third output signals of said current mirror circuit being adjusted in current value by said variable resistance.