Process-compensated HBT power amplifier bias circuits and methods
The present disclosure relates to a system for biasing a power amplifier. The system can include a first die that includes a power amplifier circuit and a passive component having an electrical property that depends on one or more conditions of the first die. Further, the system can include a second die including a bias signal generating circuit that is configured to generate a bias signal based at least in part on measurement of the electrical property of the passive component of the first die.
1. A system for biasing a power amplifier, the system comprising:
a first die including a power amplifier circuit, a semiconductor resistor, and an isolation feature, the power amplifier circuit including a transistor formed on a semiconductor, the semiconductor resistor formed from one or more layers as a layer stack device on the semiconductor that includes the transistor, the isolation feature configured to isolate the semiconductor resistor from the transistor, the semiconductor resistor configured to sense a beta parameter of the power amplifier circuit, the beta parameter dependent on characteristics of the first die; and
a second die including a bias signal generating circuit that is configured to generate a bias signal based at least in part on a measurement of the beta parameter sensed by the semiconductor resistor of the first die.
2. The system of claim 1 wherein the first die includes a heterojunction bipolar transistor (HBT) die, and the second die includes a silicon die.
3. The system of claim 2 wherein the semiconductor resistor is formed from a portion of the HBT die.
4. The system of claim 3 wherein the semiconductor resistor is formed from a base material of the HBT die.
5. The system of claim 1 wherein the semiconductor resistor has a resistance value that is approximately proportional to a temperature of the first die.
6. The system of claim 3 wherein the bias signal generating circuit includes a V-I circuit configured to provide a reference current to the semiconductor resistor, the reference current having a value that depends on the resistance of the semiconductor resistor.
7. The system of claim 6 wherein the V-I circuit provides the reference current based on a PTAT reference voltage that is substantially independent of the one or more conditions of the first die.
8. The system of claim 6 wherein the V-I circuit is further configured to generate the bias signal based on the reference current drawn by the semiconductor resistor.
9. A wireless device comprising:
a transceiver configured to process RF signals;
an antenna in communication with the transceiver configured to facilitate transmission of an amplified RF signal;
a power amplifier including a transistor formed on a semiconductor of a first die, the power amplifier connected to the transceiver and configured to generate the amplified RF signal, the first die including a semiconductor resistor and an isolation feature, the semiconductor resistor formed from one or more layers as a layer stack device on the semiconductor that includes the transistor, the isolation feature configured to isolate the semiconductor resistor from the transistor, the semiconductor resistor configured to sense a beta parameter of the power amplifier, the beta parameter dependent on characteristics of the first die; and
a bias circuit disposed on a second die and interconnected to the power amplifier, the bias circuit configured to generate a bias signal for the power amplifier based at least in part on a measurement of the beta parameter sensed by the semiconductor resistor of the first die.
10. A power amplifier module comprising:
a packaging substrate configured to receive a plurality of components;
a first die mounted on the packaging substrate, the first die including a power amplifier circuit, a semiconductor resistor, and an isolation feature, the power amplifier circuit including a transistor formed on a semiconductor, the semiconductor resistor formed from one or more layers as a layer stack device on the semiconductor that includes the transistor, the isolation feature configured to isolate the semiconductor resistor from the transistor, the semiconductor resistor configured to sense a beta parameter of the power amplifier circuit, the beta parameter dependent on characteristics of the first die; and
a second die mounted on the packaging substrate and interconnected with the first die, the second die including a bias signal generating circuit that is configured to generate a bias signal based at least in part on a measurement of the beta parameter sensed by the semiconductor resistor of the first die.
11. The power amplifier module of claim 10 wherein the first die includes a III-V semiconductor die mounted on the packaging substrate, the first die including an HBT having a selected layer above a sub-collector layer, the semiconductor resistor having a resistive layer disposed laterally from, and electrically isolated from the selected layer, the resistive layer and the selected layer formed from substantially the same material.
12. The power amplifier module of claim 11 wherein the selected layer includes a base layer.
13. The power amplifier module of claim 11 wherein the selected layer includes a sub-collector layer.
14. The power amplifier module of claim 11 wherein the semiconductor resistor further includes electrical contact pads disposed on the resistive layer to yield a resistance value for the semiconductor resistor.
15. The power amplifier module of claim 11 wherein the semiconductor resistor is connected to a circuit located outside of the first die.
16. The power amplifier module of claim 11 wherein the semiconductor resistor is configured to be sensitive to a change in one or more conditions associated with the selected layer of the HBT.
17. The system of claim 1 wherein the semiconductor resistor is a substitute for a thin-film resistor.
18. The wireless device of claim 9 wherein the semiconductor resistor is a substitute for a thin-film resistor.