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Optimal Design Of CMOS Op-Amp Using Geometric Programming
| Content Provider | Semantic Scholar |
|---|---|
| Author | Agrawal, Deepak Tripathi, Abhishek Vardhani, Harsh |
| Copyright Year | 2012 |
| Abstract | The problem of CMOS op-amp circuit sizing is addressed here. Given a circuit and its performance specifications, the goal is to automatically determine the device sizes in order to meet the given performance specifications while minimizing a cost function, such as a weighted sum of the active area and power dissipation. The approach is based on the observation that the first order behavior of a MOS transistor in the saturation region is such that the cost and the constraint functions for this optimization problem can be modeled as posynomial in the design variables. The problem is then solved efficiently as a convex optimization problem. Second order effects are then handled by formulating the problem as one of solving a sequence of convex programs. Numerical experiments show that the solutions to the sequence of convex programs converge to the same design point for widely varying initial guesses. This strongly suggests that the approach is capable of determining the globally optimal solution to the problem. Accuracy of performance prediction in the sizing program (implemented in MATLAB) is maintained by using a newly proposed MOS transistor model and verified against detailed SPICE simulation. INTRODUCTION The current trend in microelectronics is to integrate a complete system that previously occupied one or more boards on one or a few chips. Although most of the functionality in an integrated system is implemented in digital circuitry, analog circuits are needed to interface between the core digital system and the real world. Analog interface circuits have, thus, become vital and indispensable parts of most digital circuits. They provide the necessary signal conditioning and modification so that they can be processed digitally. Interface circuits span a wide variety of functions and applications such as data acquisition systems, A/D and D/A converters, particle and radiation detection circuits, automotive electronics, biomedical instrumentation and control circuits, robot sensing, industrial process monitoring, implantable biomedical instruments, preamplifiers, compressors, power drivers, etc. Therefore, to realize an integrated system on a single chip, the digital and analog circuits are combined together. This integration of analog and digital circuits results in so called mixed-signal integrated circuits. Though in an integrated system, the analog circuitry occupies a small physical area compared to the digital counterpart and becomes the bottleneck in design time reduction. The main reason for this is that the number of performance functions in an analog circuit is much larger than that in a digital circuit. Further, analog performances are very sensitive to the design variables and variation in the performance across the design space is quite high. Increase of design complexity and, at the same time, demand of design cycle time reduction due to highly competitive market can be managed only by the use of computer aided design. CAD tools specifically made to analog integrated circuit design promise to improve the design process in a variety of ways:-1) By shortening design times: 2) By simplifying the design process: 3) By improving the likelihood of error-free designs from the first fabrication run: 4) By reducing design and production cost: 5) By improving manufacturing yield: 6) By allowing easier tracking of fabrication processe Design Formulation for Two-Stage CMOS OP-AMP Sizing Two stage refers to the number of gain stages. First gain stage is a differential input single ended output stage. The second gain stage is normally a common source gain stage that has an active load. Capacitor Cc is included to ensure stability when the op-amp is used with feedback. Because Cc is between the input and the output of the high gain second stage, it is often called Miller capacitance. Since it’s effective capacitive load on the first stage is larger than its physical value In the class of two-stage op-amps, there is a basic structural similarity, namely the hierarchical structure of different configurations is the same. It is only the sub circuits, which are the leaf cells of the hierarchy that are different across the various topologies. A two-stage op-amp consists of an input stage, a second stage, and a compensating circuit. The input stage has three parts:-Harsh Vardhani, Deepak Agrawal, Abhishek Tripathi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 6, NovemberDecember 2012, pp.343-346 344 | P a g e 1. Current Source, 2. Differential Pair 3. Current Mirror. The second stage has two parts:-1. Transconductance Amplifier |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.ijera.com/papers/Vol2_issue6/BA26343346.pdf |
| Alternate Webpage(s) | http://ijera.com/papers/Vol2_issue6/BA26343346.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
