The use of portable devices is increasing day by day. Mainly these devices play a vital role in medical field when the doctors are unavailable. In that one of the important emergency medical portable systems is Electro Cardiogram (ECG). ECGs are used to measure the abnormalities of the heart by performing electrical activities. It can be done by attaching electrodes on the body for few minutes. To collect the information from electrodes data acquisition system is used in ECGs or in any biomedical systems. The major challenge in implementing data acquisition system is the increase in power dissipation due to the excessive contact impedance of electrodes. As a solution to this, A CMOS 12 lead ECG data acquisition circuit is designed by using analog multiplexers is proposed in this paper. The proposed system is designed by using improved DTMOS based analog multiplexers and these works with a power supply of ±0.2 V with a dynamic voltage range from 1uv to 200mv with the Power dissipation of 140 nW.