Abstract: A delta-sigma modulator includes two integrators. One of the two integrators is lossy. The lossy integrator may be a continuous-time integrator, or a discrete-time integrator. Use of the lossy integrator maintains stability of the delta-sigma converter over a relatively wide range of input signals.

Abstract: A frequency-to-current converter operative to convert a clock frequency to an output current is described; the frequency-to-current converter ensures that the output current increases linearly with the clock frequency. The frequency-to-current converter may be incorporated in analog-to-digital converters driven by clocks with variable frequencies. The frequency-to-current converter employs an integrator circuit, used to compare an input reference voltage and a current feedback into a sampling capacitor. At steady state, the feedback current is just sufficient to discharge the sampling capacitor to a fixed voltage. The core of the frequency-to-current conversion circuit includes one opamp, two capacitors, one feedback transistor and a few switches.

Abstract: A frequency-to-current converter operative to convert a clock frequency to an output current is described; the frequency-to-current converter ensures that the output current increases linearly with the clock frequency. The frequency-to-current converter may be incorporated in analog-to-digital converters driven by clocks with variable frequencies. The frequency-to-current converter employs an integrator circuit, used to compare an input reference voltage and a current feedback into a sampling capacitor. At steady state, the feedback current is just sufficient to discharge the sampling capacitor to a fixed voltage. The core of the frequency-to-current conversion circuit includes one opamp, two capacitors, one feedback transistor and a few switches.