Integrated bias reference
View Patent ↗An improved integrated bias reference provides a temperature and supply stable bias for devices such as radio frequency amplifiers with less complexity and expense than conventional bias references. The bias reference may be integrated onto a single GaAs die with other active circuitry such as an amplifier.
1. A bias reference comprising:
an enable supply voltage input;
a constant voltage reference circuit coupled to the enable supply voltage input, the constant voltage reference circuit comprising a proportional-to-absolute-temperature (PTAT) current source summed with a Vbe current source and a constant voltage output referenced to the enable supply voltage input;
a current conveyor circuit coupled to the constant voltage output, the current conveyor circuit comprising an input stage comprising a differential amplifier and an output stage comprising a supply transistor driving a reference transistor; and
a bias reference output coupled to the current conveyor circuit.
2. The bias reference of claim 1 , wherein the constant voltage reference circuit and the current conveyor circuit comprise NPN transistors but no PNP transistors.
3. The bias reference of claim 1 , further comprising a bias adjustment circuit coupled to the current conveyor circuit.
4. The bias reference of claim 3 , wherein the bias adjustment circuit comprises a transistor coupled to a digital to analog converter.
5. The bias reference of claim 1 , wherein the bias reference output couples to a base connection of an amplifier.
6. The bias reference of claim 1 , wherein the supply transistor is an emitter follower transistor with a collector connected to a power supply voltage input.
7. The bias reference of claim 1 , wherein the enable supply voltage is a digital logic input.
8. An integrated bias reference comprising:
a GaAs substrate;
a constant voltage reference circuit fabricated on the substrate and comprising a proportional-to-absolute-temperature (PTAT) current source summed with a Vbe current source and a constant voltage output;
a current conveyor circuit fabricated on the substrate and coupled to the constant voltage output, the current conveyor circuit comprising an input stage comprising a differential amplifier and an output stage comprising a supply transistor driving a reference transistor; and
a bias reference output coupled to the current conveyor circuit.
9. The integrated bias reference of claim 8 , further comprising a bias adjustment circuit fabricated on the substrate and coupled to the current conveyor circuit.
10. The integrated bias reference of claim 9 , wherein the bias adjustment circuit comprises a bias adjustment enable input coupled to a current sink.
11. The integrated bias reference of claim 10 , wherein the bias adjustment enable input comprises a digital logic enable input.
12. The integrated bias reference of claim 10 , wherein the current sink comprises a transistor coupled to the bias adjustment enable input and a resistor coupled to the transistor.
13. The integrated bias reference of claim 8 , wherein the supply transistor is an emitter follower transistor with a collector connected to a power supply input for supplying power supply base current to the reference transistor and the bias reference output.
14. An integrated bias reference comprising:
a GaAs substrate;
a constant voltage reference circuit fabricated on the substrate and comprising a temperature independent voltage output;
an input stage fabricated on the substrate and coupled to the temperature independent voltage output, the input stage comprising a replicated temperature independent voltage node;
a plurality of bias adjustment circuits fabricated on the substrate and coupled to the replicated temperature independent voltage node;
a reference transistor fabricated on the substrate and coupled to the replicated temperature independent voltage node; and
a bias reference output coupled to the reference transistor.
15. The integrated bias reference of claim 14 , wherein each bias adjustment circuit includes a bias adjustment enable input.
16. The integrated bias reference of claim 15 , wherein the constant voltage reference circuit is coupled to an enable supply voltage input.
17. The integrated bias reference of claim 15 , wherein the temperature independent voltage output is referenced to the enable supply voltage input.
18. The integrated bias reference of claim 14 , further comprising a supply transistor fabricated on the substrate and coupled to the reference transistor and to a supply voltage input.