Current conveyor based filter design for biomedical signals

Biomedical signals are noisy signals with a small amplitude and specturum in the region of low frequencies. In the analysis of biomedical signals, filters designed with operational amplifiers (Op-amps) are usually used. As an alternative to Op-amps, current conveyors have been presented and it has been determined that they have many advantages over Op-amps. In this study, a notch filter and a high-pass, low-pass and band-pass filter were designed to suppress network noise for an EEG signal using both a current conveyor and an Op-amp. Second generation current conveyor (CCII) and second generation current controlled current conveyor (CCCII) circuits were used as current conveyors. The cut-off frequency is 0.5 Hz for high-pass filter circuits, 100 Hz for low-pass filter circuits, and 0.5-30 Hz for band-pass filter circuits. ORCAD Pspice program was used for the design of these filter circuits and simulation results were obtained. Raw EEG data of epilepsy and healthy people taken from Bonn University were applied to the input of the designed filters. As a result of applying the EEG signal to these designed filters, Fourier Analysis was applied to the signals in the Pspice environment, and changes in the signals and EEG waves (δ, θ, α, β, γ) were examined. In addition, the application circuit of these filter circuits was made and oscilloscope images were taken at some frequency values. In practice, LM741 was used in the operational amplifier circuit and AD844 was used in the current conveyor circuit. It has been found that damping is better in filter circuits designed with a current conveyor than in the Op-amp circuit for both signals in the Pspice environment and oscilloscope images. The filter circuits designed for this purpose will be used in EEG measurements and it has been predicted that the current conveyor (CCII, CCCII+) filter circuit will provide better results in the diagnosis of diseases such as Epilepsy.