Bandgap voltage reference circuit

A voltage reference circuit comprising:

• an operational amplifier circuit;
• first and second resistor elements;
• first and second diodes;
• first and second transistors;
• and
• an output circuit receives the output of said operational amplifier circuit to output an output voltage,
• wherein said first resistor element and said first diode are connected in series between a first input terminal of said operational amplifier circuit and a reference level node,
• wherein said second resistor element and said second diode are connected in series between a second input terminal of said operational amplifier circuit and the reference level node,
• wherein said first transistor is connected between a power supply node and said first input terminal of said operational amplifier circuit,
• wherein said first transistor has a control electrode receiving an output of said operational amplifier circuit,
• wherein said second transistor is connected between the power supply node and said second input terminal of said operational amplifier circuit;
• wherein said second transistor has a control electrode receiving the output of said operational amplifier circuit,
• wherein said output circuit includes:
• a third resistor;
• a third diode;
• and
• a third transistor,
• wherein said third resistor and said third diode are connected in series between an output node outputting said output voltage and the reference level node,
• wherein said third transistor is connected between said output node and the power supply node, and receives the output of said operational amplifier circuit on a control electrode thereof, and
• wherein a temperature coefficient of said output voltage is substantially set to zero by adjusting a value of n13·R13·ln(n11·n12)/(R12−n12·R11) to approximately 23.25, where R11 and R12 are resistance values of said first and second resistor elements, n11 is a ratio of an area of a p-n junction of said second diode to an area of a p-n junction of said first diode, n12 is a ratio of a W/L ratio of said first transistor to a W/L ratio of said second transistor, R13 is a resistance value of said third resistor element, n13 is a ratio of a W/L ratio of said third transistor to the W/L ratio of said second transistor, and W/L is a gate width to a gate length ratio.

A voltage reference circuit comprising:

• first and second transistors of a same conductivity type, each having a source connected to a power source terminal;
• a first resistor element receiving a first current from a drain of the first transistor;
• a first diode receiving a current at an anode terminal from the first resistor;
• a second resistor element receiving a second current from a drain of the second transistor;
• a second diode receiving a current at an anode terminal from the second resistor;
• an operational amplifier circuit including each transistor of at least an input stage including an enhancement-type transistor, the operational amplifier receiving, at an inverted input, a signal from a first node connected between the first transistor and the first resistor, the operational amplifier receiving, at a non-inverted input, a signal from a second node connected between the second transistor and the second resistor;
• an output terminal receiving an output from one of the first node and the second node,
• wherein said first transistor and second transistor each have a control electrode receiving an output of the operational amplifier circuit,
• wherein a temperature coefficient of at least one of voltages of said first and second input terminals of said operational amplifier circuit is substantially set to zero, and wherein the temperature coefficient of at least one of voltages of the inverted and non-inverted inputs of the operational amplifier circuit is substantially set to zero by adjusting a value of R12·ln(n11·n12)/(R12−n12·R11) to approximately 23.25, where R11 and R12 are resistance values of said first and second resistor elements, n11 is a ratio of an area of a p-n junction of said second diode to an area of a p-n junction of said first diode, n12 is a ratio of a W/L ratio of said first transistor to a W/L ratio of said second transistor, and W/L is a gate width to a gate length ratio.