This paper describes a new first-and second-order delta-sigma modulator concept where the first integrator is extracted and implemented by a frequency modulator with the modulating signal as the input. The result is a simple delta-sigma modulator with no need for digital-to-analog converters, allowing straight-forward multi-bit quantization. Without the frequency modulator, the circuit becomes a frequency-to-digital converter with delta-sigma noise shaping. An experimental first-and

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... modulator have been implemented in a 1.2-¼m standard digital CMOS process and the results confirm the theory. For the first-order modulator an input signal amplitude of 150mV resulted in a SQNR of ³115dB at 2MHz sampling frequency and signal bandwidth 500Hz.