Abstract: A signal line driving circuit with power control for selectively reducing internal power dissipation when driving an external load. While driving the external load with a constant current the output voltage generated across such load is monitored. If the load impedance decreases sufficiently to cause the output voltage to fall below a predetermined threshold value and, therefore, cause the voltage across the signal line driving circuit to increase, the magnitude of the power supply voltage is automatically reduced, thereby reducing the voltage across the signal line driving circuit. Such a signal line driving circuit is particularly advantageous as a subscriber line interface circuit (SLIC). As the subscriber goes from an on-hook condition to an off-hook condition and if the subscriber loop is sufficiently short (or low in impedance), a lower power supply voltage is used to minimize the power dissipation of the SLIC while still maintaining the required subscriber loop current.

Abstract: A closed feedback loop controls the slicing, or detecting, of an incoming data signal. Detected signal information about the positive and negative peaks of the incoming data signal is processed to generate positive and negative peak reference signals which serve as reference signal levels for establishing the thresholds at which signal slicing takes place.

Abstract: A switched capacitor filter circuit having reduced offsets and providing offset compensation when used in a closed feedback loop includes a chopper stabilized amplified filter circuit which amplifies and low pass filters its input data signal to produce an output signal with an out of band signal frequency component which is at the chop signal frequency and represents an offset and 1/f noise of the chopper stabilized amplified filter circuit. An output switched capacitor filter circuit which is synchronized with the chopper stabilized amplified filter circuit filters this signal with a stopband filter frequency response that virtually eliminates such out of band signal frequency component. When used in a closed feedback loop, this filtered signal is used to generate an offset compensation signal that corresponds to the residual offset within the output signal resulting from the amplifying and filtering of the input data signal.