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US 7,453,252 B1Granted
Circuit and method for reducing reference voltage drift in bandgap circuits
AssigneeNational Semiconductor Corporation
InventorDavid J. Megaw
Life of this patent
Estimating the term…
Abstract
A circuit includes a bandgap core and a bandgap amplifier. The bandgap core is capable of receiving an input voltage and generating an output voltage. A second-order temperature coefficient in the output voltage is at least partially reduced by the bandgap core while a first-order temperature coefficient in the output voltage remains substantially unchanged.
Claims13
A bandgap core, comprising:
- a first transistor capable of receiving an input voltage;
- a first resistor coupled to the first transistor;
- a second resistor and a third resistor coupled in series to the first transistor;
- a second transistor coupled to the first resistor;
- a third transistor coupled to the third resistor;
- a fourth resistor coupled between a base and a second terminal of the second transistor;
- and
- a fifth resistor coupled to a base of the third transistor and not coupled to the base of the second transistor,
- wherein a resistance of the fourth resistor is given by a formula of:
- R
- 1
- ≈
- C
-
- (
- T
- )
- kT
- 2
- 2
-
-
- q
-
- ln
-
- (
- K
- )
- ·
- R
- 0
- R
- Δ
- 2
- ·
- T
- N
- β
- N
-
- (
- γ
- 2
- -
- γ
- 1
- )
- where R1 represents the resistance of the fourth resistor, C(T) represents a curvature of an output voltage of the bandgap core, k represents Boltzmann's constant, T represents a temperature in Kelvin, q represents a charge of an electron, R0 represents a resistance of the first and second resistors, RΔ represents a resistance of the third resistor, β represents a normalized current gain of the second and third transistors, TN represents a normalized temperature in Kelvin, γ1 represents a second-order temperature coefficient associated with the fourth resistor, and γ2 represents a second-order temperature coefficient associated with the fifth resistor.
46 more elements
A bandgap circuit, comprising:
- a bandgap core capable of receiving an input voltage and generating an output voltage, wherein a second-order temperature coefficient in the output voltage is at least partially reduced by the bandgap core while a first-order temperature coefficient in the output voltage remains substantially unchanged;
- and
- a bandgap amplifier coupled to the bandgap core, wherein the bandgap core comprises:
- a first transistor capable of receiving the input voltage;
- a first resistor coupled to the first transistor;
- a second resistor and a third resistor coupled in series to the first transistor;
- a second transistor coupled to the first resistor;
- a third transistor coupled to the third resistor;
- a fourth resistor coupled to a base of the second transistor;
- and
- a fifth resistor coupled to a base of the third transistor, wherein a resistance of the fourth resistor is given by a formula of:
- R
- 1
- ≈
- C
-
- (
- T
- )
- kT
- 2
- 2
-
-
- q
-
- ln
-
- (
- K
- )
- ·
- R
- 0
- R
- Δ
- 2
- ·
- T
- N
- β
- N
-
- (
- γ
- 2
- -
- γ
- 1
- )
- where R1 represents the resistance of the fourth resistor, C(T) represents a curvature of an output voltage of the bandgap core, k represents Boltzmann's constant, T represents a temperature in Kelvin, q represents a charge of an electron, R0 represents a resistance of the first and second resistors, RΔ represents a resistance of the third resistor, β represents a normalized current gain of the second and third transistors, TN represents a normalized temperature in Kelvin, γ1 represents a second-order temperature coefficient associated with the fourth resistor, and γ2 represents a second-order temperature coefficient associated with the fifth resistor.
48 more elements
Dependencies are inferred from the claim text.