Design and analysis of current-mode sequential logic circuits

number: 
1620
English
Degree: 
Author: 
Munaf Shakir Mahmood Al-Tememy
Supervisor: 
Dr. Ali Abdul-Jabbar Ati
year: 
2006
Abstract:

The current-mode technique is regarded as the best solution for the mixed analog and digital systems. The analysis and design of sequential logic circuits depending on this technique is considered in this project. In this technique all the input, output signals are current instead of voltage signals. The high level (logic 1) will be represented by 90μA, while the low level (logic 0) will be represented by near 0μA (1-5 μA). The basic unit of the current-mode circuits is the current-mode inverter. The current-mode logic gates (AND, OR, NAND, NOR) have been constructed from the inverter basic unit. The designed gates have been compared with the corresponding ones in voltage-mode from the power supply current and the number of transistors point of view. New type of circuits has been suggested under name current-distributor. These circuits have been used to distribute the current signals in the current-mode circuits. The designed current-mode gates have been represented by logic symbols and stored in a library within OrCAD 9.2 simulation program, in order to make the design of the complicated circuits easier. This library has been used to store the current-mode gates and circuits. The analysis and design of the current-mode sequential logic circuits have been done by using the designed current-mode gates stored in the designed current-mode library, which includes SR-Latch, SR Flip-Flop, D Flip-Flop, and JK Flip-Flop. The Latches and Flip-flops are considered as the basic unit of the sequential logic circuits. The current-mode counters and shift registers have been designed and constructed using the designed current-mode gates and flip-flops. The designed counters and shift registers are: 4-stages Asynchronous counter, 4-stages Synchronous counter, BCD counter, Up/Down BCD counter, Ring counter, Parallel IN-Serial OUT shift register, Serial INParallel OUT shift register, and Parallel IN-Parallel OUT shift register. The current mode Sequential Comparator circuit which combines between the sequential and combinational circuits has been designed as a case study. The designed current-mode circuits consume nearly constant current from the power supply, this feature is regarded as a solution for the substrate coupling noise in the mixed analog and digital system.