| 摘要 |
An analogue to digital conversion unit (208, 210) comprises three analogue to digital converters (ADCs) (300, 301, 302) having different dynamic ranges. A lowest dynamic range ADC (300) and middle dynamic range ADC (301) have saturation detectors SAT for outputting a signal when the amplitude of an input analogue signal reaches their respective dynamic ranges and saturates them. The middle dynamic range ADC (301) and highest dynamic range ADC have enable inputs EN for switching themselves on. The output of the saturation detector SAT of the lowest dynamic range ADC (300) is connected to the enable input EN of the middle dynamic range ADC (301). The output of the saturation detector SAT of the middle dynamic range ADC (301) is connected to the enable input EN of the highest dynamic range ADC (302). So, whilst the middle and the highest dynamic range ADCs (301, 302) are normally switched off, when the lowest dynamic range ADC becomes saturated, the middle dynamic range ADC (301) is switched on; and when the middle dynamic range ADC (301) is saturated, the highest dynamic range ADC (302) is switched on. The input analogue signal is therefore converted to a digital output using the ADC (300, 301, 302) having the lowest sufficient dynamic range and the higher dynamic range ADCs (301, 302) are switched off unless needed.
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