Curvature correction circuit for a voltage reference

In a voltage reference circuit for providing a reference voltage over a predetermined temperature range, the reference voltage varying within the predetermined temperature range, a circuit for reducing the variation in the magnitude of the reference voltage, the circuit comprising:

• a correction circuit means responsive to temperature for providing an output signal, said output signal being approximately zero at a predetermined temperature within the predetermined temperature range and said output signal having a value other than zero, but of the same sense, above and below said predetermined temperature within the predetermined temperature range;
• means responsive to said correction circuit means for producing a correction voltage over the predetermined temperature range, said correction voltage being combined with the reference voltage to reduce variations in the magnitude therein over the predetermined temperature range;
• a first circuit producing a correction signal having a minimum magnitude at the predetermined temperature;
• a second circuit means responsive to said correction signal for providing said output signal, said output signal being uni-directional over the predetermined temperature range of the voltage reference circuit;
• a first transistor including a control electrode for receiving a bias voltage, a first electrode coupled to an output for providing said output signal of said second circuit means, and a second electrode coupled to an input of said second circuit means for receiving said correction signal;
• a second transistor including a control electrode and a first electrode coupled to said input of said second circuit means, and a second electrode coupled to a terminal of a first power supply;
• a third transistor including a control electrode coupled to said input of said second circuit means, a first electrode coupled to said output of said second circuit means, and a second electrode coupled to said terminal of said first power supply;
• a fourth transistor including a control electrode and a first electrode coupled to said control electrode of said first transistor, and a second electrode;
• a first resistor coupled between a terminal of a second power supply and said control electrode of said first transistor;
• and
• a second resistor coupled between said second electrode of said fourth transistor and said terminal of said first power supply, said fourth transistor, first resistor, and second resistor generating said bias voltage.

A voltage reference circuit for providing a reference voltage within a predetermined temperature range, the voltage reference circuit comprising:

• a bandgap reference circuit for providing an output voltage, said output voltage being a maximum at a predetermined temperature within the predetermined temperature range;
• a first circuit providing a correction current that varies linearly with temperature, said correction current having an approximately constant temperature coefficient over the predetermined temperature range and wherein the magnitude of said correction current being a minimum at said predetermined temperature;
• a second circuit means responsive to said correction current for providing an output current, said output current being uni-directional over said predetermined temperature range;
• means responsive to said second circuit means for producing a correction voltage over said predetermined temperature range, said correction voltage being added to said output voltage of said bandgap reference to generate the reference voltage.

A circuit for providing a correction signal to a voltage reference, the voltage reference providing a reference voltage over a predetermined temperature range, the circuit comprising:

• a first circuit having an output for providing a correction current, said first circuit comprising:
• a first transistor of a first conductivity type including a control electrode, a first electrode coupled to said output of said first circuit, and a second electrode;
• a second transistor of said first conductivity type including a control electrode, a first electrode, and a second electrode coupled to said second electrode of said first transistor, a differential input voltage being applied across said control electrodes of said first and second transistors;
• a current source for biasing said first and second transistors, said current source having a terminal coupled to a terminal of a first power supply, and a second terminal coupled to said second electrode of said first transistor;
• a third transistor of a second conductivity type including a control electrode and a first electrode coupled to said first electrode of said second transistor, and a second electrode coupled to a terminal of a second power supply;
• and
• a fourth transistor of said second conductivity type including a control electrode coupled to said first electrode of said second transistor, a first electrode coupled to said output of said first circuit, and a second electrode coupled to said terminal of said second power supply;
• a second circuit means having an input for receiving said correction current and an output for providing an output current, said second circuit means comprising:
• a fifth transistor of said second conductivity type including a control electrode for receiving a bias voltage, a first electrode coupled to said output of said second circuit means, and a second electrode coupled to said input of said second circuit means;
• a sixth transistor of said second conductivity type including a control electrode and a first electrode coupled to said input of said second circuit means, and a second electrode coupled to said terminal of said second power supply;
• and
• a seventh transistor of said second conductivity type including a control electrode coupled to said input of said second circuit means, a first electrode coupled to said output of said second circuit means, and a second electrode coupled to said terminal of said second power supply;
• and
• means responsive to said second circuit means for producing a correction voltage over the predetermined temperature range, said correction voltage being combined with the reference voltage of the voltage reference.

A circuit for providing a correction signal to a voltage reference, the voltage reference providing a reference voltage over a predetermined temperature range, the circuit comprising:

• a first circuit having an output for providing a correction current, said first circuit comprising:
• a first transistor of a first conductivity type including a control electrode, a first electrode coupled to said output of said first circuit, and a second electrode;
• a second transistor of said first conductivity type including a control electrode, a first electrode, and a second electrode coupled to said second electrode of said first transistor a differential input voltage being applied across said control electrodes of said first and second transistors;
• a current source for biasing said first and second transistors, said current source having a terminal coupled to a terminal of a first power supply, and a second terminal coupled to said second electrode of said first transistor;
• a third transistor of a second conductivity type including a control electrode and a first electrode coupled to said first electrode of said second transistor, and a second electrode coupled to a terminal of a second power supply;
• and
• a fourth transistor of said second conductivity type including a control electrode coupled to Said first electrode of said second transistor, a first electrode coupled to said output of said first circuit, and a second electrode coupled to said terminal of said second power supply;
• a second circuit means having an input for receiving said correction current and an output for providing an output current, said second circuit means comprising:
• a fifth transistor of said second conductivity type including a control electrode for receiving a bias voltage, a first electrode coupled to said output of said second circuit means, and a second electrode coupled to said input of said second circuit means;
• a sixth transistor of said second conductivity type including a control electrode and a first electrode coupled to said input of said second circuit means, and a second electrode coupled to said terminal of said second power supply;
• and
• a seventh transistor of said second conductivity type including a control electrode coupled to said input of said second circuit means, a first electrode coupled to said output of said second circuit means and a second electrode coupled to said terminal of said second power supply;
• means responsive to said second circuit means for producing a correction voltage over the predetermined temperature range, said correction voltage being combined with the reference voltage of the voltage reference;
• a first resistor coupled between said terminal of said first power supply and said control electrode of said second transistor;
• a second resistor coupled between said control electrode of said first transistor and said control electrode of said second transistor;
• a third resistor coupled between said control electrode of said first transistor and said terminal of said second power supply, said first, second, and third resistors forming a resistor divider for generating said differential input voltage;
• an eighth transistor of said second conductivity type including a control electrode and a first electrode coupling to said control electrode of said fifth transistor, and a second electrode;
• a fourth resistor coupled between said first terminal of said first power supply and said control electrode of said fifth transistor;
• and
• a fifth resistor coupled between said second electrode of said eighth transistor and said terminal of said second power supply, said eighth transistor, fourth resistor, and fifth resistor generating said bias voltage.