A method for the analysis of transistor circuits having multiple DC solutions

The paper deals with circuits containing bipolar and MOS transistors. Both BJTs and MOSFETs are characterized by the Ebers–Moll-type models composed of two diodes and two current-controlled current sources. The basic and still open question of finding multiple DC solutions is discussed. To find all the DC solutions, the diodes are considered as piecewise-linear and represented by the series connection of an ideal diode, a voltage source and a linear resistor. Thus, the ideal diodes are the only nonlinear elements of the circuits. To find all the DC solutions, a method having combinatorial nature is applied. The main achievements of the paper are new algorithms enabling us to discard a huge number of combinations of the ideal diodes states immediately, without any solving of equations, or by performing a considerably reduced amount of computation. The method guarantees finding all the DC solutions of the piecewise-linear circuits. Next, each of the obtained solutions is corrected in succession by means of a controlled SPICE simulation. Four numerical examples of circuits containing bipolar and MOS transistors are presented, showing the efficiency of the proposed approach.