The Research And Design Of Current Differencing Transconductance Amplifier-based Field Reconfigurable Analog Array And Its Generated High-order Filters

In recent years,microelectronics products is being replaced faster and faster and people look forward to better service and experience.As an essential part of microelectronics products,integrated circuits need constantly to improve its performance to satisfy the market.The current differencing transconductance amplifier(CDTA)is a new type of current-mode device,and its inputs and outputs are all currents variables.It has the advantages of input terminal is virtual ground,low input impedance,high output impedance and wide bandwidth also.So,the CDTAs are widely used in designing filters,oscillators,high-speed rectifier circuit and other analog signal processing circuit.The Field Programmable Analog Array(FPAA)is a new type of integrated circuit similar to Field Programmable Gate Array(FPGA).Change of the state of internal programmable switch can lead to the structure,parameters,the function of changes of the circuit.The FPAAs are environmentally-adapted circuits.It can change the structure of circuit quickly and flexibly and they have a wide range of applications,including industrial control,aerospace,intelligent medical and other fields.In this paper,the research status of CDTA and FPAA are introduced.The FPAA based on CDTA is studied and designed.This type of FPAA inherits the characteristics of high bandwidth and operating frequency and low transmission loss of current-mode circuit.At the same time,we have designed some filter circuits based on the FPAA.The main innovations work can be summarized as follows:(1)A novel FPAA which based on CDTA and transimpedance amplifier(TIA)is proposed.First,a programmable transconductance amplifier(OTA)and a current differential unit(CDU)with multiple outputs are designed.The CDTA is implemented by a combination of CDU and programmable OTA.On this basis,a new configurable analog block(CAB)is designed using CDTA and TIA,and a FPAA is built with this CAB.The FPAA consists of nine CABs,and the CABs are connected by meshed vertical and horizontal lines.The state of each node in the mesh is controlled by a programmable switch.The proposed FPAA is verified by Cadence with Charted 0.18?m CMOS process.The results show that the designed FPAA can generate the current-mode third-order low-pass,high-pass and band-pass filter by programming.Moreover,the bandwidth of low-pass and high-pass filter can reach 40MHz and these filters are both adjustable,with a range from 1 to 40MHz.The center frequency of third-order bandpass filter can varied from 4.51MHz to 38.56MHz,and the bandwidth can varied from 2.57MHz to 20.51MHz.(2)Three different types filters with finite frequency transmission zeros which based on the designed FPAA are proposed.These filters are based on an indirect simulation of the passive RLC ladder network of the corresponding filter.The bandwidth,center frequency and transmission zero ?o of each type of filter can be achieved by changing the transconductance value gm of the programmable OTA.The filter with finite frequency transmission zeros is simulated and analyzed by using the Charted 0.18?m CMOS process in the Cadence Virtuoso ADE environment.The simulation results show that the proposed low-pass,high-pass and band-pass filter with finite frequency transmission zeros offers good performance.The operating frequency of the filter can varied from 1 to 40MHz.