Gate drivers for stacked transistor amplifiers
Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are possible where the amplifier is configured to operate in at least an active mode and a standby mode. Circuital arrangements can reduce bias circuit and stacked transistors standby current during operation in the standby mode and to reduce impedance presented to the gates of the stacked transistors during operation in the active mode while maintaining voltage compliance of the stacked transistors during both modes of operation.
1. A method for biasing a transistor stack for operation according to at least a first mode and a second mode, the method comprising:
during the first mode of operation, providing biasing voltages to gates of the transistors of the stack, except an input transistor, via high impedance nodes of a first resistive ladder network; and
during the second mode of operation, providing biasing voltages to said gates via low impedance nodes of a second resistive ladder network;
wherein
a ratio of a current through the second resistive ladder network during the second mode of operation and a current through the first resistive ladder network during the first mode of operation is equal to, or larger than, 100.
2. The method according to claim 1 , further comprising:
based on the providing, coupling during the first mode of operation a respective first biasing voltage to each of said gates; and
coupling during the second mode of operation a respective second biasing voltage to each of said gates that is substantially equal to the respective first biasing voltage.
3. The method according to claim 1 , further comprising:
based on the providing, coupling during the first mode of operation a respective first biasing voltage to each of said gates; and
coupling during the second mode of operation a respective second biasing voltage to each of said gates,
wherein for at least one gate of said gates, the respective first biasing voltage is different from the respective second biasing voltage.
4. The method according to claim 1 , wherein:
the first mode of operation is a standby mode, and
the current through the first resistive ladder network during the first mode of operation is equal to, or less than, 3 μA.
5. The method according to claim 4 , wherein:
the second mode of operation is an active mode, and the current through the second resistive ladder network during the second mode of operation is as large as 0.8 mA.
6. The method according to claim 1 , wherein:
the high impedance nodes are provided via nodes of the first resistive ladder network comprising a plurality of series connected resistors with resistance values according to desired impedance values of the high impedance nodes.
7. The method according to claim 1 , wherein:
the low impedance nodes are provided via nodes of the second resistive ladder network comprising a plurality of series connected resistors with resistance values according to desired impedance values of the low impedance nodes.
8. The method according to claim 1 , wherein:
the transistor stack comprises one or more gate capacitors each connected between a gate of a transistor of the transistor stack, except an input transistor of the transistor stack, and a reference voltage.
9. The method according to claim 8 , wherein each said one more gate capacitor is configured to allow a gate voltage at the gate of the transistor to vary along with a radio frequency (RF) voltage at a drain of the transistor.
10. The method according to claim 9 , wherein the one or more gate capacitors are configured to substantially equalize an output RF voltage at a drain of an output transistor of the transistor stack across a plurality of transistors of the transistor stack.
11. A circuital arrangement comprising:
a transistor stack configured to operate as an amplifier, the transistor stack comprising a plurality of stacked transistors comprising an input transistor and an output transistor; and
a biasing circuit coupled to one or more gates of the plurality of stacked transistors, the biasing circuit comprising a plurality of resistors,
wherein the plurality of resistors are arranged according to a first plurality of series connected resistors that define one or more high impedance nodes of a first resistive ladder network and a second plurality of series connected resistors that define or more low impedance nodes of a second resistive ladder network,
wherein the circuital arrangement is configured to operate in at least a first mode and a second mode of operation,
wherein during the first mode of operation, the one or more high impedance nodes of the biasing circuit are coupled to the one or more gates to provide respective biasing voltages,
wherein during the second mode of operation, the one or more low impedance nodes of the biasing circuit are coupled to the one or more gates to provide respective biasing voltages, and
wherein a ratio of a current through the second resistive ladder network during the second mode of operation to a current through the first resistive ladder network during the first mode of operation is equal to, or larger than, 100.
12. The circuital arrangement according to claim 11 , wherein:
for each of the one or more gates, the respective biasing voltage provided during the first mode of operation is substantially equal to the respective biasing voltage provided during the first mode of operation.
13. The circuital arrangement according to claim 11 , wherein:
for at least one of the one or more gates, the respective biasing voltage provided during the first mode of operation is different from the respective biasing voltage provided during the first mode of operation.
14. The circuital arrangement according to claim 11 , wherein the one or more low impedance nodes are coupled to the one or more gates via respective one or more switches.
15. The circuital arrangement according to claim 11 , wherein the one or more high impedance nodes are coupled to the one or more gates via respective one or more switches.
16. The circuital arrangement according to claim 11 , wherein:
the first mode of operation is a standby mode, and
the first plurality of series connected resistors are configured to conduct a current through the first resistive ladder that is equal to, or less than, 3 μA.
17. The circuital arrangement according to claim 16 , wherein:
the second mode of operation is an active mode,
the second plurality of series connected resistors are configured to conduct a current through the second resistive ladder that is as large as 0.8 mA.
18. The circuital arrangement according to claim 11 , wherein:
the transistor stack comprises one or more gate capacitors each connected between a gate of a transistor of the transistor stack except an input transistor of the transistor stack, and a reference voltage.
19. The circuital arrangement according to claim 18 , wherein each said one or more gate capacitor is configured to allow a gate voltage at the gate of the transistor to vary along with a radio frequency (RF) voltage at a drain of the transistor.
20. The circuital arrangement according to claim 19 , wherein the one or more gate capacitors are configured to substantially equalize an output RF voltage at a drain of an output transistor of the transistor stack across a plurality of transistors of the transistor stack.
21. The circuital arrangement according to claim 11 , wherein the circuital arrangement is monolithically integrated using a fabrication technology comprising one of: a) silicon-on-insulator (SOI) technology, and b) silicon-on-sapphire technology (SOS).
22. An electronic module comprising the circuital arrangement of claim 11 .