The ECG circuit consists of a signal sensing part and a processing part combined together to produce an output waveform of significant amplitude. The sensing part is made up of the ECG electrodes. The ECG electrodes sense the tiny electrical changes on skin that are caused when the heart muscle depolarizes during each heartbeat. The actual waveform obtained from the sensors is of very low amplitude i.e. in the range of millivolts. Hence the need for amplification arises. The detected waveform may also have noise components due to patient's motion, muscle tremors or power line interference. Hence to filter out these noise components filtering circuits are implemented.