Start-up circuit for bandgap reference
A start-up circuit for a bandgap reference circuit include an operational amplifier and a diode coupled to a second input terminal of the operational amplifier. The circuit includes a first current branch including a first transistor and a second transistor in series, for generating a first current in response to an output voltage at an output terminal of the operational amplifier and a second current branch including a third transistor and a fourth transistor in series, for generating a second current in response to the output voltage. The circuit further includes a resistor coupled in parallel to the fourth transistor, an inverter coupled to a connection node between the third and fourth transistors, for inverting a voltage at the connection node and generating an inversion voltage, and a fifth transistor for controlling a switching element flowing a reference current proportional to the voltage with the negative temperature coefficient in response to the inversion voltage.
1. A reference voltage generation device comprising:
a bandgap reference circuit having a first branch including a first transistor, a first resistor and a first diode in series, suitable for generating a first current, a second branch including a second transistor and a second diode in series, suitable for generating a second current, and an output circuit suitable for generating a bandgap voltage based on the sum of the first and second currents; and
a start-up circuit suitable for starting-up the bandgap reference circuit,
wherein the start-up circuit includes:
a replica diode for the second diode;
an operational amplifier including a first input terminal coupled to the second diode, a second input terminal coupled to the replica diode, and an output terminal;
a first current branch including a third transistor and a fourth transistor in series between a power supply terminal and a ground terminal, suitable for generating a first current in response to an output voltage at the output terminal of the operational amplifier;
a second current branch including a fifth transistor and a sixth transistor in series between the power supply terminal and the ground terminal, suitable for generating a second current in response to the output voltage at the output terminal of the operational amplifier;
a second resistor coupled in parallel to the sixth transistor;
an inverter coupled to a connection node between the fifth transistor and the sixth transistor, suitable for inverting a voltage at the connection node and generating an inversion voltage; and
a seventh transistor suitable for controlling the second transistor in response to the inversion voltage.
2. The reference voltage generation device of claim 1 , further comprising: a pull-up device suitable for pulling up the output voltage towards a power supply voltage.
3. The reference voltage generation device of claim 2 , wherein the pull-up device includes at least one pull-up resistor coupled between the power supply terminal and the output terminal of the operational amplifier.
4. The reference voltage generation device of claim 2 , wherein the pull-up device includes at least one current source coupled between the power supply terminal and the output terminal of the operational amplifier.
5. The reference voltage generation device of claim 1 , further comprising: a capacitor coupled between the power supply terminal and the ground terminal.
6. The reference voltage generation device of claim 1 , further comprising:
a bias generator suitable for generating a bias voltage and providing the fourth and sixth transistors with the bias voltage.
7. The reference voltage generation device of claim 6 , wherein the bias generator includes:
a third resistor; and
a diode-connected transistor in series between the power supply terminal and the ground terminal, the diode-connected transistor suitable for generating the bias voltage.
8. The reference voltage generation device of claim 1 , wherein the inverter includes a skew inverter coupled between the power supply terminal and the ground terminal, suitable for receiving a voltage at the connection node, inverting the voltage at the connection node and generating the inversion voltage to the seventh transistor.
9. The reference voltage generation device of claim 8 , wherein the inverter includes:
an eighth transistor including a first terminal coupled to the power supply terminal, a second terminal for receiving the voltage at the connection node, and a third terminal coupled to the seventh transistor, for generating the inversion voltage; and
a ninth transistor including a first terminal coupled to the seventh transistor, for generating the inversion voltage, a second terminal for receiving the voltage at the connection node, and a third terminal coupled to the ground terminal.
10. The reference voltage generation device of claim 8 , wherein the inverter further includes a diode-connected transistor coupled between the power supply terminal and the skew inverter.