A Symbolic Analysis Method Using Signal Block Diagrams and Its Application to Bias Synthesis of Analog Circuits

Hideyuki KAWAKITA  Seijiro MORIYAMA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A   No.3   pp.502-509
Publication Date: 1994/03/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on the 6th Karuizawa Workshop on Circuits and Systems)
Category: Computer Aided Design (CAD)
block diagram,  symbolic analysis,  signal propagation,  numerical method,  design procedure,  bias synthesis,  

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In this paper, an efficient and robust circuit parameter determination method suitable for analog circuit synthesis is presented. The method uses block diagram representation of circuits as implicit design knowledge. Circuit parameter determination is carried out by propagating known values along signal flow in the block diagram. The circuit parameter determination using signal propagation performs successfully when unknown circuit parameters can be solved in one way. However, when the block diagram involves implicit calculation, the propagation stops before all unknown parameters are determined. In order to cope with this problem, we introduced a method that employs a symbolic analysis technique combined with a numerical method. When the propagation of known values stops, one of unknown signals is selected, a unique symbol is assigned to the selected signal, and the signal propagation is restarted. This operation is repeated until there is no unknown signal. When the symbol propagation reaches the signal where the signal value is already set, one nonlinear equation for the signal is obtained by equating both signal values. It can be solved by a numerical method, such as Newton's method. The parameter determination method using procedural description is superior to the optimization based method because it is straightforward to incorporate design knowhow in the description. However, it is burdensome for designers to develop design procedures for each circuit to be synthesized. Because the block diagram based calculation method can be used as subroutine calls during the design procedure development, it simplifies the design procedural description and lowers the burden of designers. The method was applied to the element value determination of bias circuits to demonstrate its effectiveness.