Bandpass Single-ended to Differential Converter Based on All-Pass Filter Delay Cell

This paper introduces an alternative method for converting a single-ended sinusoidal periodic signal into a fully differential signal. The presented method features inherent band-pass frequency response and eliminates the need for output common-mode regulation. By incorporating the bandpass characteristic and omitting the common-mode regulation, the design can reduce the number of active components, thereby decreasing circuit power consumption and complexity. The generation of the complementary “inverted” signal is based on the utilization of a time delay cell based either on a transmission line or active all-pass filters. The adoption of active all-pass filters enables target a wide frequency range with either a monolithic CMOS implementation or implementation based on the standard discrete components. The direct coupling between the input and output allows for the generation of an output common mode that corresponds to the input signal’s common mode voltage. The paper introduces the basic principles of single-ended to fully differential converters, presents the architecture of the band-pass converter, describe transformation of all-pass filter frequency characteristic to the bandpass frequency characteristic, and provides experimental results. The intended application is related to signal quality conditioning in scientific instrumentation.