Unity direct chain with feedback series impedance based innovative negative group delay circuit

An innovative negative group delay (NGD) circuit theory on unity direct chain (UDC) topology is developed in this paper. The NGD UDC cells are based on the operational amplifier adder with feedback series impedance. Innovative topologies of high-pass NGD UDC cell composed of RL-series network, all-pass RC-parallel network and low-pass RC-series network are identified. It is a first time that all-pass NGD original topologies are defined. NGD analyses and synthesis methods of each NGD UDC cells are provided. The UDC cell based NGD functions are validated with SPICE simulations. The proofs-of-concept (POC) of UDCs behave as all-pass and low-pass NGD functions with group delay equal to −1 ms at very low frequencies. The low-pass NGD cut-off frequency is 424 Hz. The high pass NGD circuit generates −1 µs at the optimal NGD frequency of about 5.15 kHz. Further analysis of the operational amplifier gain and bandwidth effects is performed. The operational amplifier gain affects significantly the NGD level and bandwidth for the all considered UDC cells. Nevertheless, only the RC-parallel feedback based UDC cell is particularly sensitive to the operational bandwidth.