Design, Simulation and Evaluation of Basic Analog and Digital CMOS Circuits
Teo Wai Loon Adrian2001 年度 卒 ／学士（工学）
Signals contain information about the physical world, sometimes directly and sometimes indirectly. For example, let us imagine listening to a radio program of a weather report. The radio generates an acoustic signal that is transmitted to us and processed by our brains. The information that we can obtain directly is 1) there is a speaker nearby 2) the volume of the speaker. The information that we obtain indirectly comes from the contents of the broadcast, the expected temperature and humidity range.
Light signals (which are actually just electro-magnectic wave signals of certain frequencies) enable us to make sense of our surroundings and also to read information from print. Heat signals give us an idea of what to wear or if the house is on fire. Signals form the input to be processed to give us information (output).In other words, someone or something must process all these input signals before we can get any useful information from it. Usually, it is more convenient to have and electronic device perform this processing. Take for example a fire sprinkler system. We could employ a person to switch the system on once he spots a fire in the building. However, it is much more convenient to have an electrical system to monitor the temperature, smoke levels and automatically turn on the sprinklers once these signals exceed a certain level. To enable electronic devices to process these signals, we must first convert them into electrical signals. The conversion process of the signal is beyond the scope of this report. Rather, it will just be assumed that these signals already exist in the electrical domain.
Signals can be divided further into two forms: analog and digital signals. Analog signals are so called because the value of the signal is analogous to the physical signal it represents. And just as the physical signal exhibits a continuous variation over its range of activity, analog signals can take on any value. The electrical circuits that are used to process these signals are called analog circuits. Digital signals on the other hand, take on only a range of quantized (or discretized) values. This signal would be represented by a series of numbers with non-infinite accuracy. The choice of number system to represent the signal greatly affects the complexity of the device used for processing it. For electrical devices, we use the binary number system as we can easily relate the low voltage state (OFF) to 0 and the high voltage state (ON) to 1. We use digital circuits to process these signals.
In this project, I will attempt to design, simulate, and evaluate basic digital and analog CMOS circuits. There are many different digital and analog circuits to choose from, and I believe the best circuits to attempt are those that are elementary enough for entry level designing, and yet instructive and representative of its family of circuits. Adders are one of the building blocks of digital arithmetic and logic units (ALU). Addition forms the basis of many processing functions, from counting to multiplication. Adder circuits that add two binary numbers are thus essential to building digital systems. Amplifiers perform some of the most fundamental tasks of analog computing, namely amplifying weak signals too small to be processed reliably. Operational amplifiers are the standard circuits used for this. Furthermore, by modifying the basic structure of the operational amplifier, we can obtain other circuits like the voltage follower, weighted summer or use it as integrator/differentiator. For these reasons, I have chose to design circuits based on adders and operational amplifiers.