Power line interference at 50 Hz and their harmonics as well as other sources of interference like; radio frequency( RF) from transmitters, electric motors, and other appliances; magnetically induced currents in lead wires, clearly possess a big problem in biopotential recording devices like electrocardiogram (ECG), the electroencephalogram (EEG), the electromyogram (EMG), and the electrooculogram (EOG).That distorts the real signal and interferes with it which make the diagnosis of different diseases not accurate. Along with these problems the need of reduction of these power line interference and RF signals is very important. To solve the power line interference as well as the other interferences, it is necessary to use an instrumentation amplifier as a main component in the suggested circuit designed for the ECG device (as an example).Active filters -include high pass filter and many low pass filters to attenuate RF signals. Additionally, safety of the patient is achieved by providing electrical isolation from the power line and the earth ground. The design of the circuit and the results were done by using a work bench program (multisimO.7) and applied practically in the laboratory then both results were compared and It was clear that this design provides an acceptable elimination of noises and interference, in addition to the design of band reject filter to delete noises at 50 Flz and mobile frequencies (from cellular phones), on the same time shows the real and clear biosignal. Without any distortion and make it more accurate and useful for right diagnosis.