UNIVERSITY OF CALIFORNIA: SCHOOL OF OPTOMETRY

Abstract

This paper discusses a group of high-speed switching circuits using the basic current-switching mode Of operation. Existing literature has described the steady-state analysis of the basic current-switching. mode in performing numerous logical combinations. The first part of this paper presents a dynamic analysis of the basic current-switching mode. In previous work the assumption has been made thatthe dynamic (cid:9) . switching characteristic of the circuit Is that of a common-base amplifier with a current step applied to the emitter. When linear analysis techniques are used to find the natural frequen-des present in the circuit, such an assumption argues that the gain-bandwidth product is the dominant natural frequency and therefore determines the switching time. This paper shows that the basic current-switching mode is really an overdriven amplifier in a common-emitter configuration. Therefore the dominant natural frequency, which determines the switching time, Is actually f, the short-circuit cutoff frequency in the common-emitter configuration. The comparison of switching-time estimates and experimental measurements,, considering only the gain-bandwidth product, often shows agreement within loss than a factor of two. The paper presents the reasons for this conformity but describes the errors introduced by considering the gain-bandwidth product alone.