Standby voltage condition for fast RF amplifier bias recovery
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 standby current during operation in the standby mode while allowing a quick recovery to normal operating conditions of the amplifier. Biasing an input transistor of the stacked transistors can be obtained by using a replica stack circuit.
1. A circuital arrangement comprising:
a first transistor stack comprising a plurality of stacked transistors comprising an input transistor and an output transistor; and
a biasing circuit comprising a second transistor stack comprising a plurality of stacked transistors comprising a first transistor and a last transistor, the biasing circuit configured to provide an input gate biasing voltage to the input transistor and to the first transistor,
wherein the biasing circuit further comprises a drain biasing circuit configured to bias a drain of the last transistor,
wherein during a first mode of operation of the circuital arrangement, the drain biasing circuit couples said drain to a first supply voltage through a current source configured to source a reference current that is conducted through the second transistor stack, and
wherein during a second mode of operation of the circuital arrangement, the drain biasing circuit couples said drain to the first supply voltage while bypassing the current source.
2. The circuital arrangement according to claim 1 , wherein:
during the second mode of operation, the drain biasing circuit couples said drain to the first supply voltage through a low impedance conduction path that does not include the current source.
3. The circuital arrangement according to claim 1 , wherein the drain biasing circuit further comprises a switch configured to selectively couple said drain to the current source or to the first supply voltage.
4. The circuital arrangement according to claim 3 , wherein the current source comprises a first node connected to the switch and a second node connected to the first supply voltage.
5. The circuital arrangement according to claim 1 , wherein the drain biasing circuit further comprises a switch configured to selectively couple said drain to the first supply voltage.
6. The circuital arrangement according to claim 5 , wherein during the first mode of operation,
the switch is closed to provide a low impedance conduction path between the first supply voltage and said drain, and
the current source is deactivated to provide a high impedance conduction path between the first supply voltage and the said drain.
7. The circuital arrangement according to claim 5 , wherein during the second mode of operation,
the switch is open to provide a high impedance conduction path between the first supply voltage and said drain, and
the current source is activated to provide a low impedance conduction path between the first supply voltage and the said drain for conduction of the reference current.
8. The circuital arrangement according to claim 1 , wherein:
during the first mode of operation, the biasing circuit generates the input gate biasing voltage based on the reference current conducted through the second transistor stack.
9. The circuital arrangement according to claim 1 , wherein:
during the first mode of operation, the biasing circuit regulates the input gate biasing voltage so that the reference current is conducted through the second transistor stack.
10. The circuital arrangement according to claim 9 , wherein the biasing circuit regulates the input gate biasing voltage based on a voltage sensed at the second transistor stack.
11. The circuital arrangement according to claim 9 , wherein the biasing circuit regulates the input gate biasing voltage based on a voltage sensed at the drain of the last transistor.
12. The circuital arrangement according to claim 1 , wherein:
during the second mode of operation, the biasing circuit generates the input gate biasing voltage for no current conducted through the first and second transistor stack.
13. The circuital arrangement according to claim 1 , wherein:
during the second mode of operation, the biasing circuit generates the input gate biasing voltage to be substantially equal to a reference ground coupled to the input transistor and the first transistor.
14. The circuital arrangement according to claim 1 , wherein:
the first mode of operation is an active mode of operation for conduction of a biasing current through the first transistor stack based on the reference current conducted through the second transistor stack, and
the second mode of operation is a standby mode for essentially no conduction of current through the first transistor stack and the second transistor stack.
15. The circuital arrangement according to claim 1 , wherein biasing voltages to gates of the plurality of stacked transistors of the second transistor stack except the first transistor during the first mode of operation are substantially equal to respective biasing voltages to the gates of the plurality of stacked transistors of the second transistor stack except the first transistor during the second mode of operation.
16. The circuital arrangement according to claim 1 , wherein biasing voltages to gates of the plurality of stacked transistors of the first transistor stack except the input transistor during the first mode of operation are substantially equal to respective biasing voltages to the gates of the plurality of stacked transistors of the first transistor stack except the input transistor during the second mode of operation.
17. The circuital arrangement according to claim 1 , wherein:
a drain of the output transistor of the first transistor stack is coupled to a second supply voltage, and
the first supply voltage is equal to the second supply voltage.
18. The circuital arrangement according to claim 1 , wherein:
a drain of the output transistor of the first transistor stack is coupled to a second supply voltage, and
the first supply voltage is different form the second supply voltage.
19. The circuital arrangement according to claim 1 , wherein:
during the first mode of operation, biasing voltages to respective gates of the plurality of stacked transistors of the second transistor stack are substantially equal to biasing voltages to the respective gates of the plurality of stacked transistors of the first transistor stack.
20. The circuital arrangement according to claim 1 , wherein:
during the second mode of operation, biasing voltages to respective gates of the plurality of stacked transistors of the second transistor stack are substantially equal to biasing voltages to the respective gates of the plurality of stacked transistors of the first transistor stack.
21. The circuital arrangement according to claim 1 , wherein:
during the first mode of operation, biasing voltages to respective gates of the plurality of stacked transistors of the second transistor stack are different from biasing voltages to the respective gates of the plurality of stacked transistors of the first transistor stack.
22. The circuital arrangement according to claim 1 , wherein:
during the second mode of operation, biasing voltages to respective gates of the plurality of stacked transistors of the second transistor stack are different from biasing voltages to the respective gates of the plurality of stacked transistors of the first transistor stack.
23. The circuital arrangement according to claim 1 , wherein a number of the plurality of stacked transistors of the second transistor stack is equal to a number of the plurality of stacked transistors of the first transistor stack.
24. The circuital arrangement according to claim 1 , wherein a number of the plurality of stacked transistors of the second transistor stack is different from a number of the plurality of stacked transistors of the first transistor stack.
25. The circuital arrangement according to claim 1 , wherein the plurality of stacked transistors of the first and second transistor stacks are floating body transistors.
26. The circuital arrangement according to claim 1 , wherein the plurality of stacked transistors of the first and second transistor stacks are body tied transistors.
27. The circuital arrangement according to claim 1 , wherein the plurality of stacked transistors of the first and/or second transistor stacks comprise a combination of body tied transistors and floating body transistors.