Tham khảo tài liệu 'advances in analog circuits part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A New Approach to Biasing Design of Analog Circuits 19 the device voltage and current are zero. Also note the difference between the two fixators Fx Vj Ij and Fx Ij Vj in Fx Vj Ij the voltage source Vj provides or consumes power and the current source Ij is inactive2 whereas in Fx Ij Vj the current source Ij provides or consumes power and the voltage source Vj is inactive. Note also the similarity between a fixator and an H-model discussed in the previous chapter. Both fixator and H-model model a port representing the existing situation of the port. The major difference however is that in a fixator the equivalent impedance Req in the H-model is replaced with a nullator stamping on the port variables. This is because in an H-model the current going through the Req is also zero making the voltage zero as well. However the replacement of Req with a nullator removes the dynamics of the terminal and fixes the port values Ij and Vj for the entire operation of the circuit whereas in the case of Req the H-model behaves normally as the Thevenin or Norton equivalent circuits behave. In fact we can think of a fixator as a snapshot of a port s behavior whereas an H-model represents the entire dynamics of the port during the circuit operation. For example take the case of two networks N1 and N2 connected through a port j as in a we can replace N1 by its H-model or alternatively we can replace it with a fixator Fx Vj Ij as shown in Fig. 4. In the later case we are bounded with fixed values of Vj and Ij for the port hence the idea of fixing the design specs is born To further expand the idea we need to look for a different role for a fixator. Notice that in Fig. 4 we replaced the linear circuit N1 or its H-model with a fixator Fx Vj -Ij . Now we can do the opposite a fixator can replace a nonlinear component or port N2 in a circuit. This is stated in Property 1. Property 1 A two-terminal component linear or nonlinear in a circuit that is biased by a current I and exhibits a
