Apparatus and method for a modified brokaw bandgap reference circuit for improved low voltage power supply
An apparatus and method for a bandgap voltage reference circuit with improved operation for a low voltage power supply. A bandgap voltage reference circuit which is operable at low power supply voltage for power supplies of 1.3V comprising of a first npn bipolar transistor, a second npn bipolar transistor, a third npn bipolar transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first, second and third p-channel MOSFET. The matched second resistor and third resistor, and the first and third npn bipolar transistor pair establishes a ΔVbe dependent current (a PTAT current), and the fourth resistor established a ΔVbe to establish a bandgap voltage of approximately 1.2V.
1. A bandgap voltage reference circuit between a power supply node and a ground node and configured for generating a reference voltage comprising:
a bandgap voltage network;
wherein said bandgap voltage network comprises:
a first npn bipolar transistor; and
a second npn bipolar transistor wherein the base of said second npn bipolar transistor and said first npn bipolar transistor are electrically coupled to provide a differential base-emitter voltage;
a feedback network providing feedback to the bandgap voltage network, wherein said feedback network comprises:
a first resistor element electrically connected at one end to the emitter of said second npn bipolar transistor; and
second resistor element electrically connected to the emitter of said first npn bipolar transistor, and to the other end of said first resistor;
a current mirror sourcing said bandgap voltage network; and
an output network function providing an output voltage,
wherein said output network function comprises:
a third npn bipolar transistor wherein the base of said third npn bipolar transistor is electrically connected to the bases of said first and second npn bipolar transistors and to the collector of said third npn bipolar transistor;
a third resistor element electrically connected to the emitter of said third npn bipolar transistor; and
a fourth resistor element electrically connected to the collector of said third npn bipolar transistor, and to an output of said bandgap voltage reference circuit.
2. The bandgap voltage reference circuit of claim 1 wherein said current mirror comprises:
a first p-channel MOSFET wherein said p-channel MOSFET gate and drain are electrically connected to said first npn bipolar transistor; and
a second p-channel MOSFET wherein said p-channel MOSFET gate is electrically connected to said first p-channel MOSFET and whose p-channel MOSFET drain is electrically connected to said second npn bipolar transistor.
3. The bandgap voltage reference circuit of claim 1 wherein said current mirror comprises two PMOS devices.
4. The bandgap voltage reference circuit of claim 1 wherein said emitter ratio of said first npn bipolar transistor and said second npn bipolar transistor is 1:M wherein M is the multiplicity factor.
5. The bandgap voltage reference circuit of claim 1 wherein said second resistor and third resistor are matched.
6. The bandgap voltage reference circuit of claim 1 wherein said first npn bipolar transistor and said third npn bipolar transistor establishes a ΔVbe dependent current, a PTAT current.
7. The bandgap voltage reference circuit of claim 1 wherein said fourth resistor established a ΔVbe to establish a bandgap voltage of approximately 1.2V.
8. The bandgap voltage reference circuit of claim 7 wherein the base voltage of the first npn bipolar transistor is expressed as a function of Vbe, ΔVbe, and said first and said second resistors
R
2
·
Δ
Vbe
R
1
+
Vbe
and the bandgap output voltage can be calculated as a function of Vbe, ΔVbe, and said first resistor, said third resistor, and said fourth resistor element
(
R
3
+
R
4
)
·
Δ
Vbe
R
1
+
Vbe
.
9. A bandgap voltage reference circuit with improved operation at low voltage power supply, the circuit comprising:
a first npn bipolar transistor;
a second npn bipolar transistor wherein the base of said second npn bipolar transistor and first npn bipolar transistor are electrically coupled providing a differential voltage in the base-emitter voltage;
a third npn bipolar transistor wherein the base of said third npn bipolar transistor is electrically connected to the base of said first npn bipolar transistor and electrically connected to the collector of said third npn bipolar transistor;
a first resistor element electrically connected to the emitter of said second npn bipolar transistor;
a second resistor element electrically connected to the emitter of said first npn bipolar transistor;
a third resistor element electrically connected to the emitter of said third npn bipolar transistor;
a fourth resistor element electrically connected to the collector of said third npn bipolar transistor;
a first p-channel MOSFET wherein said p-channel MOSFET gate and drain are electrically connected to said first npn bipolar transistor;
a second p-channel MOSFET wherein said p-channel MOSFET gate is electrically connected to said first p-channel MOSFET and whose p-channel MOSFET drain is electrically connected to said second npn bipolar transistor;
a third p-channel MOSFET wherein said p-channel MOSFET gate is electrically connected to said second p-channel MOSFET and whose p-channel MOSFET drain is electrically connected to said fourth resistor; and,
a bandgap voltage reference output wherein said bandgap voltage reference output is connected to said third p-channel MOSFET drain, and said fourth resistor; and,
wherein said base voltage of the first npn bipolar transistor is expressed as a function of Vbe, ΔVbe, and said first and said second resistors
R
2
·
Δ
Vbe
R
1
+
Vbe
and the bandgap output voltage can be calculated as a function of Vbe, ΔVbe, and said first resistor, said third resistor, and said fourth resistor element
(
R
3
+
R
4
)
·
Δ
Vbe
R
1
+
Vbe
.
10. The bandgap voltage reference circuit of claim 9 wherein said emitter ratio of said first npn bipolar transistor and said second npn bipolar transistor is 1:M wherein M is the multiplicity factor.
11. The bandgap voltage reference circuit of claim 10 wherein said second resistor and third resistor are matched.
12. The bandgap voltage reference circuit of claim 11 wherein said first npn bipolar transistor and said third npn bipolar transistor establishes a ΔVbe dependent current (a PTAT current) wherein the base voltage of the first npn bipolar transistor is expressed as a function of Vbe, ΔVbe, and said first and said second resistors
R
2
·
Δ
Vbe
R
1
+
Vbe
.
13. The bandgap voltage reference circuit of claim 12 wherein said fourth resistor established a ΔVbe to establish a bandgap voltage of approximately 1.2V.
14. The bandgap voltage reference circuit of claim 12 wherein the base voltage of the first npn bipolar transistor is expressed as a function of Vbe, ΔVbe, and said first and said second resistors
R
2
·
Δ
Vbe
R
1
+
Vbe
and the bandgap output voltage can be calculated as a function of Vbe, ΔVbe, and said first resistor, said third resistor, and said fourth resistor element
(
R
3
+
R
4
)
·
Δ
Vbe
R
1
+
Vbe
.
15. A bandgap voltage reference circuit with improved operation at low voltage power supply, the circuit comprising:
a first npn bipolar transistor;
a second npn bipolar transistor wherein the base of said second npn bipolar transistor and first npn bipolar transistor are electrically coupled;
a third npn bipolar transistor wherein the base of said third npn bipolar transistor is electrically connected to the base of said first npn bipolar transistor and electrically connected to the collector of said third npn bipolar transistor;
a first resistor element electrically connected to the emitter of said second npn bipolar transistor;
a second resistor element electrically connected to the emitter of said first npn bipolar transistor;
a third resistor element electrically connected to the emitter of said third npn bipolar transistor;
a fourth resistor element electrically connected to the collector of said third npn bipolar transistor;
a first pnp bipolar transistor wherein said first pnp bipolar transistor base and collector are electrically connected to said first npn bipolar transistor;
a second pnp bipolar transistor wherein said second pnp bipolar transistor base is electrically connected to said first pnp bipolar transistor and electrically connected to said second npn bipolar transistor;
a third pnp bipolar transistor wherein said third pnp bipolar transistor base is electrically connected to said second pnp bipolar transistor and electrically connected to said fourth resistor; and,
a bandgap voltage reference output wherein said bandgap voltage reference output is connected to said third pnp bipolar transistor, and said fourth resistor; and,
wherein said base voltage of the first npn bipolar transistor is expressed as a function of Vbe, ΔVbe, and said first and said second resistors
R
2
·
Δ
Vbe
R
1
+
Vbe
and the bandgap output voltage can be calculated as a function of Vbe, ΔVbe, and said first resistor, said third resistor, and said fourth resistor element
(
R
3
+
R
4
)
·
Δ
Vbe
R
1
+
Vbe
.
16. A method of a bandgap voltage reference circuit is comprising
providing a bandgap voltage reference circuit comprises a first npn bipolar transistor, a second npn bipolar transistor, a third npn bipolar transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first, second and third p-channel MOSFET;
forming a emitter ratio of 1:M for said first and said second npn bipolar transistors;
matching said second resistor and said third resistor;
establishing a Δ Vbe dependent current from said first and third npn bipolar transistor;
establishing a Δ Vbe with said fourth resistor; and,
calculating a bandgap output voltage as a function of Vbe, ΔVbe, and said first resistor, said third resistor, and said fourth resistor
(
R
3
+
R
4
)
·
Δ
Vbe
R
1
+
Vbe
.
17. The method of claim 16 wherein said first, second and third npn bipolar transistors are homo-junction bipolar transistors.
18. The method of claim 16 wherein said first, second, and third npn bipolar transistors are hetero-junction bipolar transistors.
19. The method of claim 16 wherein said first, second, and third p-channel MOSFET are LDMOS transistors.
20. The method of claim 18 wherein said hetero-junction bipolar transistors are silicon germanium (SiGe).
21. The method of claim 18 wherein said hetero-junction bipolar transistors are silicon germanium carbon (SiGeC).
22. The method of claim 18 wherein said hetero-junction bipolar transistors are gallium arsenide (GaAs).
23. The method of claim 18 wherein said hetero-junction bipolar transistors are indium phosphide (InP).