Device for detecting the peak value of a signal
A device for detecting the peak value of a signal with crest factor not known a priori includes a pair of peak detectors, each of which includes a rectifier element and a discharge-current generator and generates a respective output signal that is a function of the ratio between a physical dimension of the rectifier element and the intensity of discharge current produced by the generator. The ratio is different for the two detectors, and a combination network combines the output signals of the two peak detectors with one another and produces a combined signal indicating the peak value sought with high accuracy.
1. A device for detecting the peak value of a signal, the device comprising:
a pair of positive peak detectors each comprising a rectifier element and a discharge element, in which each of said detectors generates a respective output signal that is a function of the ratio between a physical dimension of the rectifier element and the intensity of discharge current produced by said discharge element, said ratio between a physical dimension and the current intensity produced being different for the two detectors of said pair;
a combination network for combining said respective output signals with one another and producing a combined signal indicating said peak value; and
a comparator for comparison of the combined signal with a constant reference threshold,
wherein said combination network comprises at least one subtractor node for subtracting said respective output signals from one another, generating a difference signal.
2. The device according to claim 1 , wherein said discharge element is a resistor or a current generator.
3. The device according to claim 1 , wherein said combination network comprises at least one adder node for adding said difference signal to the output signal of one of said peak detectors of said pair.
4. The device according to claim 3 , further comprising a gain stage set between said subtractor node and said adder node.
5. The device according to claim 3 , wherein said adder node is supplied with the output signal of the peak detector that has the smaller ratio between said physical dimension of the rectifier element and the intensity of discharge current.
6. The device according to claim 1 , wherein said rectifier element is an FET and said physical dimension is constituted by the channel width or by the ratio between said width and the channel length.
7. The device according to claim 1 , wherein said combination network comprises two substantially similar differential-amplifier stages.
8. The device according to claim 7 , wherein said differential-amplifier stages have different gains.
9. A peak detector comprising:
a first positive peak detector path for generating a first output signal that is a function of the W/L ratio of a first rectifier element;
a second positive peak detector path for generating a second output signal that is a function of the W/L ratio of a second rectifier element;
a combination network for combining said first and second output signals and producing a combined output signal indicating a peak value; and
a comparator for comparison of the combined output signal with a constant reference threshold,
wherein said combination network comprises at least one subtractor node for subtracting said respective output signals from one another, generating the combined output signal.
10. The peak detector according to claim 9 , wherein said first and second peak detector paths comprise a discharge element.
11. The peak detector according to claim 9 , wherein said combination network comprises at least one adder node.
12. The peak detector according to claim 11 , further comprising a gain stage set between said subtractor node and said adder node.
13. The peak detector according to claim 11 , wherein said adder node is supplied with the output signal of the peak detector.
14. The peak detector according to claim 9 , wherein said first and second peak detector paths comprise a rectifier element.
15. The device according to claim 9 , wherein said combination network comprises two substantially similar differential-amplifier stages.
16. The device according to claim 15 , wherein said differential-amplifier stages have different gains.