Apparatuses and methods for providing constant current
An apparatus is described comprising a bandgap reference circuit comprising: an amplifier including first and second inputs and an output; and a bandgap transistor coupled to the output of the amplifier at a control electrode thereof, the bandgap transistor being further coupled commonly to the first and second inputs of the amplifier at a first electrode thereof to form a feedback path. The apparatus further comprises a resistor coupled to the first electrode of the bandgap transistor.
1. An apparatus comprising:
a bandgap reference circuit comprising:
an amplifier including first and second inputs and an output; and
a bandgap transistor coupled to the output of the amplifier and the first and second inputs of the amplifier at an electrode thereof to form a feedback path, wherein the feedback path includes first and second transistors having respective gates coupled to the output of the amplifier;
an output transistor coupled to the output of the amplifier and configured to provide a first current that is constant relative to changing temperature;
a current mirror circuit coupled to the bandgap transistor and further coupled to the output transistor to receive the first current, the current mirror circuit configured to provide a current mirror signal that is based on the first current provided by the bandgap transistor.
2. The apparatus of claim 1 , wherein the bandgap transistor is configured to provide the feedback path with a second current that is proportional to temperature, and the bandgap transistor is further configured to provide a first resistor with a third current that is complementary to temperature.
3. The apparatus of claim 2 , wherein the first current is equal to a sum of the second and third currents.
4. The apparatus of claim 1 , wherein the current mirror circuit comprises a current mirror transistor configured to receive the first current.
5. The apparatus of claim 1 , wherein the current mirror circuit comprises a current mirror transistor and current mirror amplifier configured to receive the first current at a non-inverting input of the current mirror amplifier.
6. The apparatus of claim 5 , wherein a source of the current mirror transistor is coupled to the output transistor and an inverting input of the current mirror amplifier.
7. The apparatus of claim 5 , wherein the current mirror amplifier is an operational transconductance amplifier.
8. The apparatus of claim 1 , wherein the feedback path comprises:
a positive feedback branch coupled to the first input of the amplifier, wherein the first input of the amplifier is a non-inverting input; and
a negative feedback branch coupled to the second input of the amplifier, wherein the second input of the amplifier is an inverting input.
9. The apparatus of claim 8 , wherein the positive feedback branch comprises a second resistor, a third resistor, and a first diode.
10. The apparatus of claim 9 , wherein the second resistor and third resistor have the same resistance values.
11. The apparatus of claim 8 , wherein the negative feedback branch comprises a fourth resistor and a second diode.
12. An apparatus comprising:
a bandgap reference circuit comprising:
an amplifier including a non-inverting input, an inverting input, and an output; and
a bandgap transistor coupled to the output of the amplifier and coupled to a feedback path of the amplifier, the feedback path comprising a positive feedback loop coupled to the non-inverting input of the amplifier, the feedback path further comprising a negative feedback loop coupled to the inverting input of the amplifier, wherein the positive feedback loop includes a first feedback transistor and the negative feedback loop includes a second feedback transistor;
an output transistor coupled to the output of the amplifier and configured to provide a first current that is constant relative to changing temperature; and
a current mirror circuit coupled to the output transistor to receive the first current and to the bandgap transistor, the current mirror circuit configured to provide a current mirror signal that is based on the first current provided by the bandgap transistor.
13. The apparatus of claim 12 , wherein the bandgap transistor is configured to provide the feedback path with a second current that is proportional to temperature, and the bandgap transistor is further configured to provide a first resistor with a third current that is complementary to temperature.
14. The apparatus of claim 12 , wherein the current mirror circuit comprises a current mirror transistor configured to receive the first current.
15. The apparatus of claim 12 , wherein the output of the amplifier is coupled to the first feedback transistor.
16. The apparatus of claim 15 , wherein the negative feedback loop comprises a second resistor coupled in series to the first feedback transistor and a third resistor.
17. The apparatus of claim 16 , wherein the positive feedback loop comprises a fourth resistor coupled in series to the ft-second feedback transistor, a fifth resistor, and the third resistor.
18. The apparatus of claim 17 , wherein the output of the amplifier is coupled to the second feedback transistor.
19. The apparatus of claim 17 , wherein a first resistance value of the second, third, fourth, and fifth resistors are the same, and different than a second resistance value of a first resistor.
20. The apparatus of claim 12 , wherein the amplifier is an operational transconductance amplifier.