Transient Analysis of Switched Current Source

Takahiro MIKI
Keisuke OKADA
Yasutaka HORIBA

IEICE TRANSACTIONS on Electronics   Vol.E75-C    No.3    pp.288-296
Publication Date: 1992/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Analog LSI and Related Technology)
current source,  current switch,  switched current source,  transient analysis,  D/A converter,  data converter,  

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A current source with current switches (switched current source) is widely used in various analog ICs. One of its typical application is data converters. This paper describes an analysis of the transient behavior of a switched current source. The analysis has clarified conditions and causes of overshooting in the output waveform. The analysis also clarifies dependence of the settling time on parameters. The waveform heavily depends on time constant and initial charge at the internal node where current source and current switch are connected. They can cause the overshooting and limit the settling time. A phenomenon of acceleration of the settling time and an influence of the charge coupling through current switches are also discussed. A chart mentioned in this paper is useful for the initial design and the improvement of switched current sources.