Apparatus and method for offset drift trimming
View Patent ↗An apparatus is provided that includes a drift trimming stage that includes a first current source providing a current with a first temperature dependency and a second current source providing a current with a second temperature dependency. The first and the second current source are coupled at a first node and configured to have equal currents at a first temperature. There is further a third current source providing a current with a third temperature dependency and a fourth current source providing a current with a fourth temperature dependency. The third current source and the fourth current source are coupled at a second node and configured to have equal currents at the first temperature. There is a first resistor coupled between the first node and a third node, a second resistor coupled between the second node and the third node. The first node and the second node are coupled to provide a combined voltage drop across the first resistor and the second resistor for reducing the offset drift.
1. An apparatus comprising:
a first node;
a second node;
a third node;
a first proportional-to-absolute-temperature (PTAT) current source that is coupled to the first node;
a first complementary-to-absolute-temperature (CTAT) current source that is coupled to the first node;
a second PTAT current source that is coupled to the second node;
a second CTAT current source that is coupled to the second node;
a first adjustable resistor that is coupled between the first node and the third node;
a second adjustable resistor that is coupled between the second node and the third node; and
a common mode voltage source that is coupled to the third node.
2. The apparatus of claim 1 , wherein the apparatus further comprises an amplifier that is coupled to the first and second nodes.
3. The apparatus of claim 2 , wherein the first and second PTAT current sources further comprise:
a PTAT current generator;
a first transistor that is coupled to the PTAT current generator and the first node; and
a second transistor that is coupled to the PTAT current generator and the second node.
4. The apparatus of claim 3 , wherein the first and second CTAT current sources further comprise:
a CTAT current generator that is coupled to the PTAT current generator;
a third transistor that is coupled to the CTAT current generator;
a current mirror that is coupled to the third transistor;
a fourth transistor that is coupled to the current mirror and the first node; and
a fifth transistor that is coupled to the current mirror and the second node.
5. The apparatus of claim 4 , wherein the apparatus further comprises a CTAT-PTAT measurement circuit that is coupled to the PTAT current generator and the current mirror.
6. An apparatus comprising:
output circuitry that receives an input signal; and
a drift trimming stage including:
a first node that is coupled to the output circuitry;
a second node that is coupled to the output circuitry;
a third node;
a first PTAT current source that is coupled to the first node;
a first CTAT current source that is coupled to the first node;
a second PTAT current source that is coupled to the second node;
a second CTAT current source that is coupled to the second node;
a first adjustable resistor that is coupled between the first node and the third node;
a second adjustable resistor that is coupled between the second node and the third node; and
a common mode voltage source that is coupled to the third node.
7. The apparatus of claim 6 , wherein the drift trimming stage further comprises an amplifier that is coupled between the first and second nodes and the output circuitry.
8. The apparatus of claim 7 , wherein the first and second PTAT current sources further comprise:
a PTAT current generator;
a first transistor that is coupled to the PTAT current generator and the first node; and
a second transistor that is coupled to the PTAT current generator and the second node.
9. The apparatus of claim 8 , wherein the first and second CTAT current sources further comprise:
a CTAT current generator that is coupled to the PTAT current generator;
a third transistor that is coupled to the CTAT current generator;
a current mirror that is coupled to the third transistor;
a fourth transistor that is coupled to the current mirror and the first node; and
a fifth transistor that is coupled to the current mirror and the second node.
10. The apparatus of claim 9 , wherein the apparatus further comprises a CTAT-PTAT measurement circuit that is coupled to the PTAT current generator and the current mirror.
11. The apparatus of claim 10 , wherein the amplifier further comprises a first amplifier, and wherein the output circuitry further comprises:
an input stage that is coupled to the first amplifier; and
a second amplifier that is coupled to the input stage.
12. The apparatus of claim 11 , wherein the current mirror further comprises a first current mirror, and wherein the input stage further comprises:
a first resistor;
a second resistor;
a second current mirror that is coupled to the first and second resistors; and
a differential pair of transistors that receives the input signal and that is coupled to the second current mirror and the first amplifier.
13. An apparatus comprising:
output circuitry that receives an input signal; and
a drift trimming stage including:
a first node that is coupled to the output circuitry;
a second node that is coupled to the output circuitry;
a third node;
a PTAT current generator having:
a first diode-connected bipolar transistor;
a first bipolar transistor that that is coupled to the base of the first diode-connected bipolar transistor;
a second bipolar transistor that is coupled to the base of the first diode-connected bipolar transistor;
a third bipolar transistor that is coupled to the collector of the first diode-connected bipolar transistor at its emitter and to the collector of the first bipolar transistor at its base;
a second diode-connected bipolar transistor that is coupled to the collector of the second bipolar transistor at its collector; and
a fourth bipolar transistor that is coupled to the base of the third bipolar transistor at its collector and to the base of the second diode-connected transistor at its base;
a CTAT current generator having:
a first resistor;
a second resistor;
a third diode-connected bipolar transistor that is coupled to the first resistor at its emitter;
a fifth bipolar transistor that is coupled to the second resistor at its emitter and to the base of the third diode-connected bipolar transistor at its base; and
a sixth bipolar transistor that is coupled to the collector of the third diode-connected bipolar transistor at its collector and to the collector of the third bipolar transistor at its base;
a seventh bipolar transistor that is coupled to the collector of the fifth bipolar transistor at its base;
a fourth diode-connected bipolar transistor that is coupled to the emitter of the seventh bipolar transistor at its collector;
an eighth bipolar transistor that is coupled to the base of the first diode-connected bipolar transistor at its base and to the first node at its collector;
a ninth bipolar transistor that is coupled to the base of the first diode-connected bipolar transistor at its base and to the second node at its collector;
a tenth bipolar transistor that is coupled to the base of the fourth diode-connected bipolar transistor at its base and to the first node at its collector;
an eleventh bipolar transistor that is coupled to the base of the fourth diode-connected bipolar transistor at its base and to the second node at its collector;
a first adjustable resistor that is coupled between the first node and the third node;
a second adjustable resistor that is coupled between the second node and the third node; and
a common mode voltage source that is coupled to the third node.
14. The apparatus of claim 13 , wherein the drift trimming stage further comprises an amplifier that is coupled between the first and second nodes and the output circuitry.
15. The apparatus of claim 14 , wherein the first and second resistors are adjustable.
16. The apparatus of claim 15 , wherein the apparatus further comprises a CTAT-PTAT measurement circuit that is coupled to the PTAT current generator.
17. The apparatus of claim 16 , wherein the amplifier further comprises a first amplifier, and wherein the output circuitry further comprises:
an input stage that is coupled to the first amplifier; and
a second amplifier that is coupled to the input stage.
18. The apparatus of claim 17 , wherein the input stage further comprises:
a current mirror; and
a differential pair of transistors that receives the input signal and that is coupled current mirror and the first amplifier.