Constant VDS1 bias control for stacked transistor configuration
Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can have a varying supply voltage. According to one aspect, the gate of the input transistor of the amplifier is biased with a fixed voltage whereas the gates of the other transistors of the amplifier are biased with variable voltages that are linear functions of the varying supply voltage. According to another aspect, the linear functions are such that the variable voltages coincide with the fixed voltage at a value of the varying supply voltage for which the input transistor is at the edge of triode. According to another aspect, biasing of the stacked transistors is such that, while the supply voltage varies, the drain-to-source voltage of the input transistor is maintained to a fixed value whereas the drain-to-source voltages of all other transistors are equal to one another.
1 . A circuital arrangement comprising:
an amplifier comprising an input transistor and a plurality of cascode transistors comprising a first cascode transistor directly connected to the input transistor, the amplifier configured to operate between a varying supply voltage and a reference ground; and
a biasing circuit configured to generate, based on the varying supply voltage, a fixed bias voltage and a plurality of varying bias voltages,
wherein
during operation of the amplifier between the varying supply voltage and the reference ground, the fixed bias voltage is provided to a gate of the first cascode transistor, and the plurality of varying bias voltages are provided to respective gates of remaining transistors of the plurality of cascode transistors,
the biasing circuit comprises a first plurality of series connected resistors coupled between the varying supply voltage and a fixed supply voltage, and
the plurality of varying bias voltages are provided at respective plurality of nodes connecting adjacent resistors of the first plurality of series connected resistors.
2 . The circuital arrangement according to claim 1 , wherein each varying bias voltage of the plurality of varying bias voltages is a linear function of the varying supply voltage.
3 . The circuital arrangement according to claim 1 , wherein the fixed bias voltage maintains operating points of the input transistor essentially constant throughout a voltage variation range of the varying supply voltage.
4 . The circuital arrangement according to claim 1 , wherein the plurality of varying bias voltages control drain-to-source voltages of the plurality of cascode transistors to be substantially equal.
5 . The circuital arrangement according to claim 1 , wherein the drain-to-source voltages of the plurality of cascode transistors are substantially equal throughout a voltage variation range of the varying supply voltage.
6 . The circuital arrangement according to claim 5 , wherein
the voltage variation range includes a low voltage, and
for decreasing values of the varying supply voltage toward the low voltage, the drain-to-source voltages of the plurality of cascode transistors gradually decrease toward zero.
7 . The circuital arrangement according to claim 6 , wherein
for a value of the varying supply voltage equal to the low voltage, the drain-to-source voltages of the plurality of cascode transistors are equal to about zero.
8 . The circuital arrangement according to claim 1 , wherein the plurality of varying bias voltages provide a substantially equal distribution of a difference between a varying voltage of the varying supply voltage and a substantially constant drain voltage of the input transistor across drain-to-source voltages of the plurality of cascode transistors.
9 . The circuital arrangement according to claim 1 , wherein each varying bias voltage of the plurality of varying bias voltages and the fixed bias voltage coincide at a value of the varying supply voltage that is substantially equal to a value for which the input transistor is at an edge of triode.
10 . The circuital arrangement according to claim 1 , wherein each varying bias voltage of the plurality of varying bias voltages is a linear function of the varying supply voltage in a range of values equal to or larger than a value for which the input transistor is at an edge of triode.
11 . The circuital arrangement according to claim 1 , further comprising a plurality of gate capacitors connected between gate terminals of respective transistors of the plurality of cascode transistors and the reference ground,
wherein each gate capacitor of the plurality of gate capacitors is configured to allow a voltage at a gate terminal of a respective transistor to vary along with a radio frequency (RF) voltage at a drain of the respective transistor.
12 . The circuital arrangement according to claim 1 , wherein
the biasing circuit further comprises a second plurality of series connected resistors coupled between the fixed supply voltage and the reference ground, and
the fixed bias voltage is provided at a respective node connecting adjacent resistors of the second plurality of series connected resistors.
13 . The circuital arrangement according to claim 12 , wherein
the respective gates of the remaining transistors are coupled to the respective plurality of nodes of the first plurality of series connected resistors, and
the gate of the first cascode transistor is coupled to the respective node of the second plurality of series connected resistors.
14 . A circuital arrangement comprising:
an amplifier comprising an input transistor and a plurality of cascode transistors comprising a first cascode transistor directly connected to the input transistor, the amplifier configured to operate between a varying supply voltage and a reference ground; and
a biasing circuit configured to generate, based on the varying supply voltage, a fixed bias voltage and a plurality of varying bias voltages,
wherein
during operation of the amplifier between the varying supply voltage and the reference ground, the fixed bias voltage is provided to a gate of the first cascode transistor, and the plurality of varying bias voltages are provided to respective gates of remaining transistors of the plurality of cascode transistors, and
the biasing circuit comprises one or more of: a) a lookup table, b) a A/D converter, c) a D/A converter, and d) an operational amplifier, for generation of the plurality of varying bias voltages.
15 . A circuital arrangement comprising:
an amplifier comprising an input transistor and a plurality of cascode transistors comprising a first cascode transistor directly connected to the input transistor, the amplifier configured to operate between a varying supply voltage and a reference ground; and
a biasing circuit configured to generate, based on the varying supply voltage, a fixed bias voltage and a plurality of varying bias voltages,
wherein
during operation of the amplifier between the varying supply voltage and the reference ground, the fixed bias voltage is provided to a gate of the first cascode transistor, and the plurality of varying bias voltages are provided to respective gates of remaining transistors of the plurality of cascode transistors, and
the varying supply voltage varies in a range from 1 volt to 5 volts.
16 . The circuital arrangement according to claim 15 , wherein the varying supply voltage varies in a range from 2.5 volts to 4.8 volts.
17 . The circuital arrangement according to claim 15 , wherein the input transistor and/or the plurality of cascode transistors are metal-oxide-semiconductor (MOS) field effect transistors (FETs), or complementary metal-oxide-semiconductor (CMOS) field effect transistors (FETs).
18 . The circuital arrangement according to claim 17 , wherein said transistors are fabricated using one of: a) silicon-on-insulator (SOI) technology, and b) silicon-on-sapphire technology (SOS).
19 . The circuital arrangement according to claim 14 , wherein the fixed bias voltage maintains operating points of the input transistor essentially constant throughout a voltage variation range of the varying supply voltage.
20 . The circuital arrangement according to claim 14 , wherein the drain-to-source voltages of the plurality of cascode transistors are substantially equal throughout a voltage variation range of the varying supply voltage.
21 . The circuital arrangement according to claim 15 , wherein the fixed bias voltage maintains operating points of the input transistor essentially constant throughout a voltage variation range of the varying supply voltage.
22 . The circuital arrangement according to claim 15 , wherein the drain-to-source voltages of the plurality of cascode transistors are substantially equal throughout a voltage variation range of the varying supply voltage.