| 摘要 |
PURPOSE: To reduce noise from an analog configuration block by using a high- degree loop filter, so as to extend a dynamic range with respect to an input signal. CONSTITUTION: A signal ui at an input 2 and a feedback signal ufb are subtracted by a differential amplifier 4, and its difference signal Ud is fed to an N-degree LPF consisting of a series of N sets of primary integrated sections 6.1-6.N. An input 8.1 of the section 6.1 receives the signal Ud, and each input of the other section receives an output of a preceding section. Each output is connected to an input of an adder 18 that generates a filter signal Uf being a sum of weight section signals via weight amplifiers 16.1-16.N. The signal Uf is quantized (20), in response to a clock signal fs, and converted into a digital signal Uo available at an output 22 and back to the amplifier 4 after a D/A conversion 24. Thus, every time a degree number of a filter means is reduced by one, and the modulation operation is made stable up to a maximum of the input signal.
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