Simultaneous Automated AC and DC Design Linear Integrated Circuit Amplifiers

Both ac and dc automated network design algorithms have been shown to be feasible and practical in the design of lumped linear networks. The present paper extends and combines these algorithms to integrated circuit amplifiers, where the ability to "grow" transistors to attain specified design goals is mandatory. In particular, it is shown that under the reasonable assumption that certain fabrication parameters are held fixed, suitable design parameters for transistors are the area and the perimeter of the emitter and the dc collector current. Transistor models can be derived in terms of these parameters. The rather general ac-dc design algorithm described allows transistors to grow to meet ac specifications; dc design requirements arise naturally. Two examples are used to show the tractability of the approach: 1 ) a differential pair of transistors is designed for given ac and dc specifications; 2) a cascade amplifier is designed for specified gain, bandwidth, and input and output impedances. The latter example requires the growth of common-base and common-collector transistors.