Abstract: The detrimental nonlinear charging currents from an analog input signal through an anti-aliasing filter into a sampling circuit can be minimized by using primary and secondary inputs to the sampling circuit. The secondary input is turned on before the primary input and the charge required to charge the parasitic capacitance inside the sampling circuit and to replenish the channeling charge lost in the previous cycle is supplied primarily through the secondary input. Immediately after the secondary input is turned off the primary input is connected to the sampling node, and only the charge required to fine tune the signal into the sampling capacitor is drawn through the primary input. Therefore, most of the non-linear charge injection is passed through the secondary input, and the signal passed through the primary input is used to fine tune the voltage levels inside the sampling circuit during the actual sampling operation.

Abstract: A low power white noise source is fabricated on an integrated circuit. The noise source includes a bipolar junction transistor (Q.sub.BJT) having an emitter terminal coupled to a common circuit potential, a collector terminal coupled to a source of current (CS), and a base terminal coupled through a resistance (R.sub.B) to a bias signal (V.sub.bias). The resistance has a resistance value selected to enhance a noise signal generated by the transistor in a collector current thereof. The noise source further includes a transresistance amplifier (AMP) having an input coupled to the collector terminal for converting the noise signal to a voltage signal (NOISE OUT) having white noise characteristics.

Abstract: A low-noise switched-capacitor DAC converts an integer number from an N-bit digital format into an analog voltage level by transferring charge between two appropriately ratioed capacitors using a plurality of switches. The switches select only an appropriate one of a plurality of capacitors to connect to an operational amplifier in accordance with any digital input. The sampled kT/C noise and switch charge injection from an N-bit DAC is thus beneficially reduced.