US 5,670,868 AGranted

Low-constant voltage supply circuit

AssigneeHitachi, Ltd.

InventorsAkisada Moriguchi, Osamu Yumoto, Masaharu Hata, Hironori Saito, Teruhisa Azumaguchi

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Abstract

A constant-voltage power source circuit includes a first current mirror circuit having a diode and a first transistor and a second current mirror circuit having at least second and third transistors, which sets a current flowing to the first current mirror circuit to be substantially equal to a current flowing to the second mirror circuit, and provides the current flowing to the second current mirror circuit to a fourth transistor that determines an output voltage. With this arrangement, a current flowing to the current mirror circuits structured by the diode and transistors is determined by a forward characteristic of the diode, and this current becomes a constant current which is hardly affected by a variation of a power source voltage. When this current flows to the two current mirror circuits including transistors and then flows to the transistor which determines an output voltage, it is possible to hold a voltage between the base and the emitter of the transistor which determines an output voltage, at substantially a constant value without being affected by a variation of the power source voltage.

Claims16

Dependent claims

A constant-voltage power source circuit comprising:

a first current mirror circuit including at least a diode and a first transistor;
and
a second current mirror circuit including at least second and third transistors;
wherein
a current which flows to said first current mirror circuit is set substantially equal to a current flowed to said second current mirror circuit, and a current flowed to said second current mirror circuit is flowed to a fourth transistor that determines an output voltage, wherein
said first current mirror circuit includes a diode, a cathode of which is connected to one of power source voltage terminal and a first NPN type transistor, a base of which is connected to an anode of said diode, and said second current mirror circuit includes second and third PNP type transistors, bases of which are connected in common,
emitters of said second and third transistors respectively of said second current mirror circuit are connected to the other power source voltage terminal, a collector of said second transistor is connected to at least a collector of said first transistor of said first current mirror circuit, and an emitter of said first transistor is connected to said first power source voltage terminal;
said collector of said first transistor is connected to a base of a fifth PNP type transistor, an emitter of said fifth transistor is connected to bases of said second and third transistors respectively, and a collector of said fifth transistor is connected to one power source voltage terminal;
a collector of said third transistor of said second current mirror circuit is connected to at least a collector of a fourth NPN type transistor, and an emitter of said fourth transistor is connected to said one power source voltage terminal;
and
a current from flowing in said collector of said second transistor of said second current mirror circuit to said collector of said first transistor of said first current mirror circuit, is set substantially equal to a current from flowing in said collector of said third transistor of said second current mirror circuit to said collector of said fourth transistor for determining an output voltage.

8 more elements

A constant-voltage power source circuit, comprising:

a first current mirror circuit including a diode, a cathode of which is connected to one of power source voltage terminals and a first NPN type transistor, a base of which is connected to an anode of said diode;
and
a second current mirror circuit including second and third PNP type transistors, bases of which are connected in common;
wherein emitters of said second and third transistors respectively of said second current mirror circuit are connected to said other power source voltage terminal, a collector of said second transistor is connected to at least a collector of said first transistor of said first current mirror circuit, and an emitter of said first transistor is connected to said one power source voltage terminal;
said collector of said first transistor is connected to a base of a fifth PNP type transistor, an emitter of said fifth transistor is connected to said bases of said second and third transistors respectively, and a collector of said fifth transistor is connected to said one power source voltage terminal;
a collector of said third transistor of said second current mirror circuit is connected to at least a collector of a fourth NPN type transistor, and an emitter of said fourth transistor is connected to said one power source voltage terminal;
a current from flowing in said collector of said second transistor of said second current mirror circuit to said collector of said first transistor of said first current mirror circuit is set substantially equal to a current from flowing in said collector of said third transistor of said second current mirror circuit to said collector of said fourth transistor for determining an output voltage;
an anode of said diode of said first current mirror circuit and a base of said first transistor are connected to an emitter of a sixth NPN type transistor, and a collector of said sixth transistor is connected to said other power source voltage terminal;
a base of said fourth transistor for determining an output voltage is connected to an emitter of a seventh NPN type transistor and is also connected to a collector of an eighth NPN type transistor, an emitter of said eighth transistor is connected to said one power source voltage terminal, and a collector of said seventh transistor is connected to said other power source voltage terminal;
at least said collector of said fourth transistor is connected to respective bases of said sixth and seventh transistors and is also connected to a base of a ninth NPN type transistor for supplying an output voltage;
a collector of said ninth transistor is connected to said other power source voltage terminal, and an emitter of said ninth transistor is connected to said one power source voltage terminal through predetermined resistor element to thereby form an output circuit, and a plurality of said output circuits are connected in parallel to both of said power source voltage terminals;
and
said first transistor is driven by a current flowed from said emitter of said sixth transistor, said fourth transistor is driven by a current flowed from said emitter of said seventh transistor, and said sixth, seventh and ninth transistors are driven by at least a collector voltage of said fourth transistor such that a plurality of same output voltages are supplied.

10 more elements

A constant-voltage power source circuit, comprising:

a first current mirror circuit including a diode, a cathode of which is connected to one of power source voltage terminals and a first NPN type transistor, a base of which is connected to an anode of said diode;
and
a second current mirror circuit including second and third PNP type transistors, bases of which are connected in common;
wherein emitters of said second and third transistors respectively of said second current mirror circuit are connected to said other power source voltage terminal, a collector of said second transistor is connected to at least a collector of said first transistor of said first current mirror circuit, and an emitter of said first transistor is connected to said one power source voltage terminal;
said collector of said first transistor is connected to a base of a fifth PNP type transistor, an emitter of said fifth transistor is connected to said bases of said second and third transistors respectively, and a collector of said fifth transistor is connected to said one power source voltage terminal;
a collector of said third transistor of said second current mirror circuit is connected to at least a collector of a fourth NPN type transistor, and an emitter of said fourth transistor is connected to said one power source voltage terminal;
a current from flowing in said collector of said second transistor of said second current mirror circuit to said collector of said first transistor of said first current mirror circuit, is set substantially equal to a current from flowing in said collector of said third transistor of said second current mirror circuit to said collector of said fourth transistor for determining an output voltage;
an anode of said diode of said first current mirror circuit and a base of said first transistor are connected to an emitter of a sixth NPN type transistor, and a collector of said sixth transistor is connected to said other power source voltage terminal;
a base of said fourth transistor for determining an output voltage is connected to an emitter of a seventh NPN type transistor and is also connected to a collector of an eighth NPN type transistor, an emitter of said eighth transistor is connected to said one power source voltage terminal, and a collector of said seventh transistor is connected to said other power source voltage terminal;
at least said collector of said fourth transistor is connected to respective bases of said sixth and seventh transistors and is also connected to a base of a ninth NPN type transistor for supplying an output voltage;
a collector of said ninth transistor is connected to said other power source voltage terminal, and an emitter of said ninth transistor is connected to said one power source voltage terminal through at least one resistor element to thereby form a plurality of output circuits having different resistance value for each of the output circuits, said plurality of said output circuits having at least series connected resistor element of different values are connected in parallel to both of said power source voltage terminals;
and
said first transistor is driven by a current flowed from said emitter of said sixth transistor, said fourth transistor is driven by a current flowed from said emitter of said seventh transistor, and said sixth, seventh and ninth transistors are driven by at least a collector voltage of said fourth transistor such that a plurality of different output voltages are supplied.

10 more elements

Dependencies are inferred from the claim text.