Amplifiers make signals bigger. Amplification is one of the basic operations of an electronic circuit. There are many kinds of amplifier designs. This section describes the operational amplifier, the building block of most analog electronics.
One of the best sources of information about analog circuit design and operational amplifiers is the design library at Analog Devices. This company is one of the leaders in analog integrated circuits. Over the years their design engineers have written great tutorials and detailed guides about their product line and, more importantly, about the fundamentals of analog design and signal sensing. This is a highly trusted source.