Schottky enhanced bias circuit
Embodiments disclosed herein relate to a bias circuit that uses Schottky diodes. Typically, a bias circuit will include a number of transistors used to generate a bias voltage or a bias current for a power amplifier. Many wireless devices include power amplifiers to facilitate processing signals for transmission and/or received signals. By substituting the bias circuit design with a design that utilizes Schottky diodes, the required battery voltage of the bias circuit may be reduced enabling the use of lower voltage power supplies.
1. A bias circuit comprising:
a first Schottky diode in electrical communication with a power amplifier;
a field effect transistor in electrical communication with the first Schottky diode;
a bipolar junction transistor in electrical communication with the field effect transistor, the field effect transistor and the bipolar junction transistor forming a feedback loop; and
a frequency compensation circuit to stabilize the feedback loop.
2. The bias circuit of claim 1 wherein the frequency compensation circuit is positioned between a gate of the field effect transistor and a base of the bipolar junction transistor.
3. The bias circuit of claim 1 wherein the frequency compensation circuit includes a resistor and a capacitor that forms a resistor capacitor circuit.
4. The bias circuit of claim 1 wherein the frequency compensation circuit is a Miller compensation circuit.
5. The bias circuit of claim 1 further including a second Schottky diode in electrical communication with the bipolar junction transistor.
6. The bias circuit of claim 5 wherein a current density of the first Schottky diode and a current density of the second Schottky diode match.
7. The bias circuit of claim 6 wherein the first Schottky diode and the second Schottky diode are sized so as to cause the current density of the first Schottky diode and the current density of the second Schottky diode to match.
8. A power amplifier module comprising:
a power amplifier;
a bias circuit including: a first Schottky diode in electrical communication with the power amplifier; a field effect transistor in electrical communication with the first Schottky diode; and a bipolar junction transistor in electrical communication with the field effect transistor, and a size of the bipolar junction transistor matching a size of the field effect transistor; and
a reference current circuit in electrical communication with the bias circuit.
9. The power amplifier module of claim 8 wherein the reference current circuit is implemented in a first material and the bias circuit is implemented in a second material.
10. The power amplifier module of claim 9 wherein the first material is silicon and the second material is gallium arsenide.
11. A power amplifier module comprising:
a power amplifier;
a bias circuit including: a first Schottky diode in electrical communication with the power amplifier; a field effect transistor in electrical communication with the first Schottky diode; and a bipolar junction transistor in electrical communication with the field effect transistor, and a size of the bipolar junction transistor matching a size of the field effect transistor; and
a power amplifier controller configured to set a bias operating current of the bias circuit.
12. A power amplifier module comprising:
a power amplifier; and
a bias circuit including: a first Schottky diode in electrical communication with the power amplifier; a field effect transistor in electrical communication with the first Schottky diode; a bipolar junction transistor in electrical communication with the field effect transistor; and a second Schottky diode in electrical communication with the bipolar junction transistor, a size of the bipolar junction transistor matching a size of the field effect transistor.
13. A power amplifier module comprising:
a power amplifier; and
a bias circuit including: a first Schottky diode in electrical communication with the power amplifier; a field effect transistor in electrical communication with the first Schottky diode; and a bipolar junction transistor in electrical communication with the field effect transistor, and a size of the bipolar junction transistor matching a size of the field effect transistor, the field effect transistor and the bipolar junction transistor forming a feedback loop.
14. A wireless device comprising:
a power amplifier module including a power amplifier and a bias circuit, the bias circuit including: a first Schottky diode in electrical communication with the power amplifier; a field effect transistor in electrical communication with the first Schottky diode; a bipolar junction transistor in electrical communication with the field effect transistor; and a power amplifier controller configured to set a bias operating current of the bias circuit; and
a matching circuit in electrical communication with the power amplifier and configured to provide a harmonic termination.
15. The wireless device of claim 14 wherein the power amplifier module further includes a reference current circuit in electrical communication with the bias circuit.
16. The wireless device of claim 15 wherein the reference current circuit is implemented in silicon and the bias circuit is implemented in gallium arsenide.
17. The wireless device of claim 14 wherein the field effect transistor and the bipolar junction transistor form a feedback loop.
18. The wireless device of claim 14 wherein the power amplifier module further includes a second Schottky diode in electrical communication with the bipolar junction transistor.
19. The wireless device of claim 18 wherein the first Schottky diode and the second Schottky diode are sized so as to cause a current density of the first Schottky diode and a current density of the second Schottky diode to match.
20. The power amplifier module of claim 11 further comprising a reference current circuit in electrical communication with the bias circuit.