A mobile phone jammer is an instrument used to prevent cellular phones from receiving signals from base stations. When used, the jammer effectively disables cellular phones. These devices can be used in practically any location, but are found primarily in places where a phone call would be particularly disruptive because silence is expected. But the existing mobile phone jammers are having several defects so the authors are going to design a new mobile phone jammer using VLSI Technology which will be more efficient than existing jammers.