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US 6,307,426 B1Granted
Low voltage, band gap reference
AssigneeSGS-Thomson Microelectronics S.A.
InventorsGiulio Ricotti, Domenico Rossi
Life of this patent
Estimating the term…
Abstract
A voltage, replica of the difference between two dissimilar base-emitter voltages in the form of an intrinsic input offset voltage of a differential input pair of transistors of a noninverting, buffer-configured operational amplifier, is summed with a pre-established fraction of a base-emitter voltage, to produce a voltage reference without thermal drift of a level that can be as low as few 10 mV. The intrinsic input offset voltage is controlled by a local feedback loop acting on the bias current that is forced through the input pair of transistors that may be realized with a certain area ratio. The relatively simple circuit is useful in battery operated, low supply voltage, systems.
Claims22
A circuit for generating a temperature stable reference voltage, said circuit comprising:
- a first circuit comprising a first bipolar transistor, and connected to provide as output a first voltage equivalent to a constant fraction, which is less than unity, of the base-emitter voltage of said first bipolar transistor;
- an operational amplifier, configured as a noninverting buffer, and operatively connected to receive said first voltage and to produce a control voltage equal to the sum of said first voltage and a predefined and controlled intrinsic offset voltage of a differential input pair of transistors of said operational amplifier and said temperature stabilized reference voltage, which is proportional to said control voltage, a first one of said differential input pair of transistors having an emitter area different from a second one of said differential input pair of transistors;
- and
- said operational amplifier having a feedback loop for controlling a bias current forced through said input pair of transistors.
1 more element
A circuit for generating a temperature stable reference voltage, said circuit comprising:
- a first circuit comprising a first bipolar transistor, and connected to provide as output a first voltage equivalent to a constant fraction, which is less than unity, of the base-emitter voltage of said first bipolar transistor;
- an operational amplifier, configured as a noninverting buffer, and operatively connected to receive said first voltage and to produce a control voltage equal to the sum of said first voltage and a predefined and controlled intrinsic offset voltage of a differential input pair of transistors of said operational amplifier and said temperature stabilized reference voltage, which is proportional to said control voltage, a first one of said differential input pair of transistors having an emitter area different from a second one of said differential input pair of transistors;
- and
- said operational amplifier having a feedback loop for controlling a bias current forced through said input pair of transistors;
- wherein said first voltage is applied to the base of a first transistor of said differential input pair;
- wherein a control resistance is connected between a collector of said first transistor of said differential input pair and ground;
- wherein said control voltage, which is present on an intermediate node of a voltage divider of said operational amplifier connected between said output voltage and ground, being applied to the base of said second transistor of said differential input pair;
- and
- wherein said feedback loop comprises a current mirror capable of forcing a pre-established current through said control resistance.
6 more elements
A circuit for generating a temperature stable reference voltage, said circuit comprising:
- a first circuit comprising a first bipolar transistor, and connected to provide as output a first voltage equivalent to a constant fraction, which is less than unity, of the base-emitter voltage of said first bipolar transistor;
- an operational amplifier, configured as a noninverting buffer, and operatively connected to receive said first voltage and to produce a control voltage equal to the sum of said first voltage and a predefined and controlled intrinsic offset voltage of a differential input pair of transistors of said operational amplifier and said temperature stabilized reference voltage, which is proportional to said control voltage, a first one of said differential input pair of transistors having an emitter area different from a second one of said differential input pair of transistors;
- and
- said operational amplifier having a feedback loop for controlling a bias current forced through said input pair of transistors;
- wherein said first voltage is applied to the base of a first transistor of said differential input pair;
- and
- wherein a control resistance is connected between a collector of said first transistor of said differential input pair and ground;
- and
- wherein said control voltage, which is present on an intermediate node of a voltage divider of said operational amplifier connected between said output voltage and ground, being applied to the base of said second transistor of said differential input pair;
- wherein said feedback loop comprises a current mirror capable of forcing a pre-established current through said control resistance;
- wherein said current mirror comprises an amplifying stage, which drives an output stage of the amplifier.
8 more elements
A method for generating a small reference voltage without thermal drift, comprising the steps of:
- (a.) generating a first voltage which is a pre-established fraction of a base-emitter junction voltage of a bipolar transistor;
- (b.) deriving a ΔVbe voltage, which corresponds to the difference between Vbe voltages of two transistors with different current densities, and
- (c.) producing a voltage proportional to the sum of said ΔVbe and said first voltage to produce an output signal.
A circuit for generating a temperature stable reference voltage, comprising:
- circuitry, including a first bipolar transistor which generates a first voltage equivalent to a constant fraction, which is less than unity, of the base-emitter voltage of said first bipolar transistor;
- and
- an operational amplifier comprising a pair of bipolar transistors, carrying two different current densities, which are connected to receive said first voltage, and to provide an output which is dependent on said first voltage and is offset corresponding to the difference between the respective base-emitter voltages of said pair of bipolar transistors;
- said output of said operational amplifier providing a temperature-independent output.
1 more element
A circuit for generating a temperature stable reference voltage, comprising:
- circuitry, including a first bipolar transistor, which generates a first voltage equivalent to a constant fraction of the base-emitter voltage of said first bipolar transistor;
- an operational amplifier connected to receive said first voltage at a first input terminal, and to provide an output signal which is dependent on both the voltage difference between said first input terminal and a second input and an offset corresponding to the difference between the respective base-emitter voltages of a pair of bipolar transistors carrying two different current densities;
- said output signal being operatively connected to provide a substantially temperature-independent reference voltage output;
- and
- said second input terminal of said operational amplifier being responsive to said output signal.
2 more elements
A circuit for generating a temperature stable reference voltage, comprising:
- a pair of transistors with two different emitter current densities;
- circuitry, including an additional bipolar transistor, connected to said pair of transistors, for driving a first one of said pair of transistors with a base drive current proportional to a divided-down fraction of the base-emitter voltage of said additional bipolar transistor;
- an amplifying stage which includes said pair of transistors, which amplifies current passed by said first one of said pair of transistors to provide a substantially temperature-independent reference voltage output;
- and
- a second one of said pair of transistors being responsive to said output signal.
2 more elements
Dependencies are inferred from the claim text.