Robotics technology to obtain information from several sensory modalities (e.g. touch, vision, hearing, etc.) is needed for robots to interact with and perceive their environment. Indeed, robots are always in physical contact with their operational environments. Many factors motivate a robot's detection of physical contact, ranging from safe robot operation around humans to robot behaviors that depend on user guidance. Tactile sensing is different from other sensory modalities, such as vision and hearing, as it requires physical contact with objects. In this paper, we focus on the domain of tactile sensing in robotics. We will introduce basic aspects of tactile sensors and our research of analog signal processing techniques.