In this paper we describe and analyze the internal noise sources of a signal charge partitioning circuit and indicate techniques for minimizing the internal noise of the circuit. Two noise sources are identified and described as a function of the circuit architecture and operating speeds: noise due to the trapping of thermal charge-density fluctuations (Johnson noise) and noise due to electrons scattered by the action of the partitioning gate. The noise due to the trapping of thermal charge-density fluctuations is dependent on the time it takes to divide the charge; at most, it is equal to the thermal Johnson noise of the integration well times the partition ratio. Noise due to the closing of the partitioning gate is dependent on the division ratio, the length of the septum gate, and its closure speed; it is, however, independent of the size of the charge packet being divided. With small division ratios (<10) and optimal operating speeds, the partition noise can be limited to fewer than 100 e-.