Low pass anti-alias filter for ADC with differential input on base Op-Amp with differential output with a minimum number of capacitors

The new circuit of third order low-pass filter (LPF) on operational amplifier (Op-Amp) with differential output designed to limit the spectrum of signals at the input of an analog-to-digital converter (ADC) is presented. The developed circuit contains one capacitor less than in classical LPF. The basic equations of the new circuit are presented and the results of computer simulation obtained in Micro-Cap CAD, which based on models of THS4130 Op-Amp by Texas Instruments, are shown. The results of computer simulation confirm the efficiency of this LPF scheme and show a close to ideal correspondence between the theoretical and real amplitude-frequency response.