The Research Of FPAA And Its Application In Signal Conditioning Circuits

Inspired by the great success of FPGA(Field Programmable Gate Array), a new type of programmable analog devices appears in recent years which named as FPAA(Field Programmable Analog Array). According to the actual needs, the internal connections and parameters of the FPAA can be changed by digital programming to achieve the desired circuit function and parameter adjustment, which is similar to the FPGA. Compared with the traditional way of analog circuit design, the design of the analog circuit using FPAA with appropriate EDA(Electronic Design Automation)tools is simpler, more convenient, and this method can shorten the product development cycle. The FPAA has a broad application prospects in a variety fields of industry automation, signal processing, wireless communications, instrumentation,aerospace, artificial neural networks, robotics and so on.The FPAA is composed of the programmable analog core unit CAB(Configurable Analog Block), Interconnection Network, Input and Output Block,Configuration data memory. A variety of implementation techniques have been applied in the FPAA, one of the mainstream technologies is based on continuous-time OTA(operational transconductance amplifier), which is also used in this paper.Besides, the intelligent signal conditioning circuit is a hot research area in the information science, it can achieve by the FPAA, this method of implementation can overcome the traditional signal conditioning circuit disadvantages such as the function is single, parameters are not adjustable and so on, it can better adapted to today’s complex industrial needs. Therefore, this paper puts into the studying of the FPAA based on an adjustable linear transconductance POTA and discussing the FPAA’s application in signal conditioning. The major research works in this paper as follows:1) In order to overcome the shortcomings of the OTA tunable range is narrow and OTA’s transconductance can not be tuned, two different types of POTA are designed in this paper, which the linear range is wider and the transconductance is adjustable. One of the linear adjustable POTA is based on signal attenuation techniques, the another is based on cross-coupling technology. Through the analysis and comparison on the two different types POTAs, the performance of the latter POTA is better, and it will serve as a basic unit applied in the subsequent circuit of FPAA unit circuit and FPAA arrays.2) The adjustable parameters of FPAA are usually realized by programmable switches capacitor matrix. To reduce the parasitic capacitance effect on the capacitormatrix, a programmable capacitance multiplier circuit based on the cross-coupling POTA is designed which can reduce the influence of parasitic parameters by using a small amount of switches, and it is easier to integrate with simpler circuit. And on this basis, combining with the cross-coupling POTA, a CAB circuit which is the core unit of FPAA is designed in this paper.3) Then a FPAA array is formed, which is achieved by using hexagonal Internet network, programmable switches and switch-sharing technology to connect multiple designed CAB circuits together. Compared with traditional FPAA array, the structure of this array is simple, it is easy to integrate, and it improves the performance of the FPAA by reducing the number of switches and effects of the switch noise.4) In order to overcome the shortcomings of the traditional signal conditioning circuit we using the FPAA to realize signal conditioning. In this paper, three common signal conditioning circuits based on FPAA are designed to illustrate the feasibility.The circuits including adjustable gain circuit, general order filters, D/A converters,and then carries the simulation and verification on them at last. The results show that the FPAA can realize corresponding signal conditioning by digitally programming,and this implementation method has the characteristics of intelligent signal processing functions with strong flexibility and adaptability.