Abstract: A CMFB circuit that contains only one voltage amplifier in the loop, and is therefore immune to multi-pole stability problems. This is accomplished by providing feedback in the form of current which sums with a constant node current of the differential voltage amplifier. This control current source is created with two transistors, one controlled by the desired, common-mode voltage level, and another connected to the actual, measured common-mode output level.

Abstract: Out-of-range comparators for an analog-to-digital converter at other than the first stage of a pipeline ADC. By using a subsequent stage, the accuracy required for the ADC is reduced. The offset voltage of these comparators are reduced when input referred through the gain of the cascade of pipeline amplifiers in front of it, thus reducing the necessary accuracy required for out-of-range indication. This results in the accuracy requirement of the out-of-range comparators being greatly reduced. ADC fault detection is possible when these out-of-range comparators are located at the output of the final stage.

Abstract: A common-mode feedback circuit which calculates the common-mode signal at each stage of a pipeline ADC, rather than calculating it globally and distributing it. The local calculation thus provides a local interpolation between the positive and negative voltage reference, and also provides a mechanism for storing the interpolated charge for application to the common-mode feedback input of the amplifier.

Abstract: A replica circuit derived from the bias generating circuit for an amplifier. The replica circuit duplicates the operating point of the op-amp transistors, and generates two reference voltages. The average of these two voltages is the optimum common-mode desired output level to maximize differential op-amp swing. Several circuits are disclosed that make use of these two voltages to set the op-amp output to the average of the two voltages.