Power supply stage

1. A method of generating a power supply tracking a reference signal, comprising the steps of:

filtering, in a plurality n of filtering steps, the reference signal, the filtering applied in each filtering step being different;

generating, in a respective plurality n of voltage generation steps, a respective plurality of intermediate voltages in dependence on the respective filtered reference signals;

receiving, in each of a plurality of n−1 voltage summation steps respectively associated with the 2 nd to n th voltage generation steps, the intermediate voltage generated in the respective generating step;

receiving, in each of the plurality of n−1 voltage summation steps the output of the preceding summation step;

generating, as an output of each summation step the sum of the two inputs; and

providing the output of the n−1 th summation step as the supply voltage.

2. The method of claim 1 wherein in successive filtering steps the filtering bandwidth is successively broadened.

3. The method of claim 1 further comprising the steps of feeding-back the output of at least one summation step to the respective generating step, wherein the generating step generates the intermediate voltage in dependence on the feed-back output.

4. The method of claim 1 further comprising the step of feeding back the intermediate voltage generated in each of the generating steps to the input of generating step of the preceding generating step to thereby reduce a dc offset.

5. An apparatus for generating a power supply tracking a reference signal, comprising:

a plurality n of voltage generation stages, each comprising:

a filter for filtering the reference signal, wherein the bandwidth of each filter is different; and

a voltage generation stage for generating an intermediate supply voltage in dependence on the filtered reference signal;

a plurality n−1 of voltage summation stages, associated with the 2 nd to n th voltage generation stages respectively, each adapted to:

receive as a first input the intermediate supply voltage generated by the respective voltage supply generation stage;

receive as a second input the output of the preceding summation stage; and

generate as an output the sum of the first and second inputs, wherein the output of the n−1 th summation stage is the output supply voltage.

6. The apparatus of claim 5 wherein in each of the plurality of filters the filtering bandwidth is successively broadened.

7. The apparatus of claim 5 further comprising a feedback stage for feeding-back the output of at least one summation step to the respective generating step, wherein the voltage generation stage generates the intermediate voltage in dependence on the feed-back output.

8. The apparatus of claim 5 further comprising a feedback stage for feeding back the intermediate voltage generated in each voltage generation stage to the input of the preceding voltage generation stage to thereby reduce a dc offset.