Hall effect switching device

Claim 2

A Hall effect switching circuit comprising in combination: a Hall effect device having two output terminals across which is developed a Hall voltage whenever appropriately oriented electric and magnetic fields are simultaneously applied thereto, a differential amplifier having differential input terminals coupled to respective output terminals of said Hall effect device and an output terminal at which is generated a current proportional to the magnitude of said Hall voltage; a trigger circuit having a pair of input terminals across which a first predetermined voltage differential must be maintained in order to produce a signal at the output terminal thereof at a first value and across which a lower second predetermined voltage differential must be maintained in order to limit said output signal to a second value; and current source means coupled with the output terminal of said differential amplifier and responsive to the magnitude of said generated current for maintaining said first predetermined voltage differential across the input terminals of said trigger circuit when said generated current is above a first predetermined level and for maintaining said second predetermined voltage differential across the input terminals of said trigger circuit when said generated current is below a second predetermined current, whereby said trigger circuit is fired and produces an output signal of the first value whenever said Hall voltage reaches a predetermined value.

Claim 3

The switching circuit as recited in claim 1 wherein said mentioned means for maintaining predetermined voltage differentials includes a variable current source coupled with the output terminal of said differential amplified and coupled to one of the input terminals to said trigger circuit and a constant current source coupled to the other of the input terminals to said trigger circuit, said variable current source generating a current proportional to the current generated by said differential amplifier.

Claim 4

The switching circuit as recited in claim 2 wherein said trigger circuit is a Schmidt trigger and wherein said differential amplifier contains transistors of one conductivity type connected so as to produce a differential current corresponding to said Hall voltage and further including a differential to signal-ended converter which generates said current proportional to said Hall voltage from the differential current generated at the collectors of said transistors.

Claim 5

A magnetically actuated switching circuit comprising in combination: means operative in response to the presence of a magnetic field of a predetermined magnitude at a location for generating a voltage proportional to the strength of the field at said location; means coupled with said voltage generating means for generating a current proportional to the magnitude of said voltage; and means coupled with said current generating means and operative in response to the magnitude of said current above a first predetermined threshold level for generating a signal and for interrupting said signal in response to the magnitude of said current falling below a second predetermined threshold, whereby the generation of said signal indicates the presence of said magnetic field at said location.

Claim 6

A magnetically actuated switching circuit comprising in combination: means operative in response to the presence of a magnetic field of a predetermined magnitude at a location for generating a voltage proportional to the strength of the field at said location; means coupled with said voltage generating means for generating a current proportional to the magnitude of said voltage; and means coupled with said current generating means and operative in response to the magnitude of said current above a first predetermined threshold level for generating a signal and for interrupting said signal in response to the magnitude of said current falling below a second predetermined threshold, whereby the generation of said signal indicates the presence of said magnetic field at said location.

Claim 7

The circuit as recited in claim 4 wherein said means for generating a signal includes a trigger circuit which is actuated by a predetermined current differential at the inputs thereto and means for varying the current available at one of said inputs in response to the magnitude of the current generated by said curreNt generating means such that said trigger circuit is actuated by the presence of said magnetic field at said location.

Claim 8

The circuit as recited in claim 5 wherein the current available at the other of the inputs of said trigger circuit is held constant such that said current differential is varied by varying the current to said one input.

Claim 9

The circuit as recited in claim 6 wherein said means for generating a voltage is a Hall effect device and wherein said voltage is the Hall voltage.

Claim 10

The circuit as recited in claim 7 wherein said means for generating a current is a differential amplifier.

Claim 11

The circuit as recited in claim 8 wherein said differential amplifier provides two currents having a difference proportional to said Hall voltage and further including a differential to single-ended current converter coupled to said two currents such that the output of said converter is said generated current proportional to the magnitude of said difference and thus the magnitude of said Hall voltage.

Claim 12

A Hall effect switch comprising: A power supply having two terminals across which a potential voltage is developed; A Hall effect device, said device having two output terminals and providing an output voltage across said terminals whenever an appropriately oriented magnetic field is applied across said device; A differential amplifier having a single-ended output current, the amplitude of said output current being proportional to the output voltage available across said terminals, said differential amplifier including: a first pair of PNP transistors having interconnected emitters, a first resistive element coupled between said interconnected emitters of said first pair and one terminal of said power supply, a first pair of NPN transistors, the bases of different transistors in said first pair of NPN transistors coupled to different output terminals of said Hall effect device, the collectors thereof coupled to said one terminal of said power supply and the emitters of different ones of said first pair of NPN transistors coupled to different bases of the transistors in said first pair of PNP transistors, second and third resistive elements coupled between the other of the terminals of said power supply and different emitters of the transistors in said first pair of NPN transistors so as to bias said last mentioned transistors into conduction, a second pair of NPN transistors having interconnected bases, having collectors coupled to different collectors of the transistors in said first pair of PNP transistors and having emitters coupled to said other terminal of said power supply, a first NPN transistor having its base coupled to the collector of one transistor in said second pair of NPN transistors, having its collector coupled to said one terminal of said power supply and having its emitter coupled to said interconnected bases, a fourth resistive element coupled between the emitter of said first NPN transistor and said other terminal of said power supply so as to form a variable current source for said interconnected bases in conjunction with said first NPN transistor, the output of said differential amplifier being at the collector of one of the transistors in said second pair of NPN transistors; A variable current source, said current source including: a third pair of NPN transistors having interconnected bases and collectors which form first and second current delivery terminals, fifth and sixth resistive elements coupled respectively between different emitters of said third pair of NPN transistors and said other terminal of said power supply, and means for establishing a fixed bias voltage at the bases of said third pair of NPN transistors, the output of said differential amplifier being coupled to the emitter of one of the transistors in said third pair of NPN transistors such that the current generated by said one transistor in saId third pair of NPN transistors is proportional to said Hall device output voltage; Trigger circuit means coupled between said first and second current delivery terminal, said trigger circuit including: a fourth pair of NPN transistors having interconnected emitters, a seventh resistive element coupled between said last mentioned interconnected emitters and said other terminal of said power supply, a fifth pair of NPN transistors having emitters coupled to the bases of different transistors in said fourth pair of NPN transistors, having their collectors coupled to said one terminal of said power supply and having their bases coupled to said first and second current delivery terminals respectively, a voltage dividing circuit coupled between said second current delivery terminal and said one terminal of said power supply, a point intermediate the ends of said voltage dividing circuit being coupled to the collector of that transistor in said fourth pair of NPN transistors whose base is connected through one of said fifth pair of NPN transistors to said first current delivery terminal, an eighth resistive element coupled between said first current delivery terminal and said one terminal of said power supply, whereby said voltage dividing circuit and said eighth resistive element provide said trigger circuit with a predetermined hysteresis, the output of said trigger circuit being available at the collector of that transistor in said fourth pair of NPN transistors which is connected through one of said fifth pair of NPN transistors to said second current delivery terminal, and a ninth resistive element coupled between said one terminal of said power supply and the collector of said last mentioned transistor in said fourth pair so as to bias it into conduction; An output stage coupled to the output of said trigger circuit including: a first PNP transistor having an emitter coupled to said one terminal of said power supply, having its base coupled to the output of said trigger circuit and having a pair of collectors, second and third NPN transistors, each having its base coupled to a different one of said pair of collectors, ninth and 10th resistive elements coupled between the bases and emitters of said second and third NPN transistors respectively, and 11th and 12th resistive elements coupled between the emitters of said second and third NPN transistors respectively and said other terminal of said power supply, whereby the output of said Hall effect switch is taken between either the collector of said second or the collector of said third NPN transistor and said one terminal of said power supply.

Claim 13

A Hall effect switch comprising: A power supply having two terminals across which a potential voltage is developed; A Hall effect device, said device having two output terminals and providing an output voltage across said terminals whenever an appropriately oriented magnetic field is applied across said device; A differential amplifier having a single-ended output current, the amplitude of said output current being proportional to the output voltage available across said terminals, said differential amplifier including: a first pair of PNP transistors having interconnected emitters, a first resistive element coupled between said interconnected emitters of said first pair and one terminal of said power supply, a first pair of NPN transistors, the bases of different transistors in said first pair of NPN transistors coupled to different output terminals of said Hall effect device, the collectors thereof coupled to said one terminal of said power supply and the emitters of different ones of said first pair of NPN transistors coupled to different bases of the transistors in said first pair of PNP transistors, second and third resistive elements coupled between the other of the terminals of said power supply and different emitters of the transistors in said first pair of NPN transistors so as to bias said last mentioned transistors into conduction, a second pair of NPN transistors having interconnected bases, having collectors coupled to different collectors of the transistors in said first pair of PNP transistors and having emitters coupled to said other terminal of said power supply, a first NPN transistor having its base coupled to the collector of one transistor in said second pair of NPN transistors, having its collector coupled to said one terminal of said power supply and having its emitter coupled to said interconnected bases, a fourth resistive element coupled between the emitter of said first NPN transistor and said other terminal of said power supply so as to form a variable current source for said interconnected bases in conjunction with said first NPN transistor, the output of said differential amplifier being at the collector of one of the transistors in said second pair of NPN transistors; A variable current source, said current source including: a third pair of NPN transistors having interconnected bases and collectors which form first and second current delivery terminals, fifth and sixth resistive elements coupled respectively between different emitters of said third pair of NPN transistors and said other terminal of said power supply, and means for establishing a fixed bias voltage at the bases of said third pair of NPN transistors, the output of said differential amplifier being coupled to the emitter of one of the transistors in said third pair of NPN transistors such that the current generated by said one transistor in saId third pair of NPN transistors is proportional to said Hall device output voltage; Trigger circuit means coupled between said first and second current delivery terminal, said trigger circuit including: a fourth pair of NPN transistors having interconnected emitters, a seventh resistive element coupled between said last mentioned interconnected emitters and said other terminal of said power supply, a fifth pair of NPN transistors having emitters coupled to the bases of different transistors in said fourth pair of NPN transistors, having their collectors coupled to said one terminal of said power supply and having their bases coupled to said first and second current delivery terminals respectively, a voltage dividing circuit coupled between said second current delivery terminal and said one terminal of said power supply, a point intermediate the ends of said voltage dividing circuit being coupled to the collector of that transistor in said fourth pair of NPN transistors whose base is connected through one of said fifth pair of NPN transistors to said first current delivery terminal, an eighth resistive element coupled between said first current delivery terminal and said one terminal of said power supply, whereby said voltage dividing circuit and said eighth resistive element provide said trigger circuit with a predetermined hysteresis, the output of said trigger circuit being available at the collector of that transistor in said fourth pair of NPN transistors which is connected through one of said fifth pair of NPN transistors to said second current delivery terminal, and a ninth resistive element coupled between said one terminal of said power supply and the collector of said last mentioned transistor in said fourth pair so as to bias it into conduction; An output stage coupled to the output of said trigger circuit including: a first PNP transistor having an emitter coupled to said one terminal of said power supply, having its base coupled to the output of said trigger circuit and having a pair of collectors, second and third NPN transistors, each having its base coupled to a different one of said pair of collectors, ninth and 10th resistive elements coupled between the bases and emitters of said second and third NPN transistors respectively, and 11th and 12th resistive elements coupled between the emitters of said second and third NPN transistors respectively and said other terminal of said power supply, whereby the output of said Hall effect switch is taken between either the collector of said second or the collector of said third NPN transistor and said one terminal of said power supply.