Multi-stage amplifier with multiple sets of fixed and variable voltage rails

A signal processing device comprising:

• a multi-stage amplifier, the amplifier comprising:
• a first amplification stage having an output node and first and second power supply nodes, wherein during operation the first and second power supply nodes of the first amplification stage are coupled to respective first and second voltage rails;
• and
• a second amplification stage, coupled to the output node of the first amplification stage, having first and second power supply nodes, wherein during operation the first and second power supply nodes of the second amplification stage are respectively coupled to a variable voltage rail and to a third voltage rail, and the first voltage rail is greater than the variable voltage rail.

A method of amplifying an input signal, the method comprising:

• receiving first and second power supply voltages with a first amplification stage of a multi-stage amplifier;
• receiving third and fourth power supply voltages with a second amplification stage of the multi-stage amplifier, wherein the first power supply voltage is greater than the third power supply voltage, the third power supply voltage varies over time during operation of the multi-stage amplifier and the first and third power supply voltages are more positive than respective second and fourth power supply voltages;
• receiving an input signal with the multi-stage amplifier;
• and
• amplifying the input signal using the multi-stage amplifier to generate an amplified input signal.

A signal processing system comprising:

• a first amplification stage, wherein during operation the first amplification stage receives a fixed supply voltage and a first variable supply voltage, and the fixed supply voltage is greater than the first variable supply voltage;
• a second amplification stage, coupled to an output of the first amplification stage, wherein during operation the second amplification stage receives the fixed supply voltage and the variable supply voltage;
• and
• a third amplification stage, coupled to an output of the second amplification stage, wherein during operation the third amplification stage receives a second variable supply voltage and the first variable supply voltage, wherein the fixed supply voltage is greater than a maximum second variable supply voltage.