ABSTRACT
Current sources are the foundation of circuit design in microelectronics. Current sources provide biasing for circuit operation. They serve as output drivers. They serve as load elements in amplifier input stages. Even logic gates can be modeled as a collection of variable current sources. Analysis of circuits in proceeding chapters will often show a resistance biasing the block under analysis. Current mirrors are used almost exclusively for this purpose in microelectronics. Current sources offer the advantages of smaller size, higher accuracy and can be designed to provide temperature coefficients of current as needed. However, resistors can and do serve well as current sources in some instances. Let us first consider the characteristics of an ideal DC current source as provided in circuit simulators such as SPICE.
