Research And Design Of Programmable Switched-Current Filter

Switched-Current(SI) technology is a novel current-mode analog sampled data signal processing technology. It is not only fully compatible with standard digital CMOS technology, but also has advantages of fine high frequency characteristic, low working voltage, high dynamic range and so on. It is a new direction of digital-analog mixedintegrated circuit after Switched-Capacitor technology.This paper mainly discussed the programmable SI filter. Firstly, the principles of SI circuits and the reasons of multifarious errors were present, then some improved methods of SI memory cell and SI integrator were given. Secondly, the synthesize and realization mothods of programmable SI filter were introduced. Finally, a kind of SI biquadratic filter with multifunction and adjustment was designed. The filter included the SI memory cell, SI integrator, current multiplier, current mirror, current divider, fiducial voltage source and fiducial current source. The main reasearch results are as follows:(1) The errors improved methods are summarized and a novel high performance Class AB SI memory cell is designed. The circuits are composed by the symmetrical flipped voltage follower and the class AB SI memory cell, with the input circuit introduces current conveyance and the output adopts a cascode. It exhibits low error, low power, high performance. Simulation indicates that the transmission error is 0.75%, clock feedthrough error is 9.0% of the basic Class AB SI memory cell, power dissipation is 37.5% of the Class A SI memory cell, and the input dynamic range is four times as the static current.(2) The existence errors of SI integrator are summarized and a fine performance SI bilinear integrator is designed. An difference structure technique is proposed to eliminate nearly all the DC offset current.(3) Using the Class AB grounded gate multiplier as basic cell to design a high linear, four quadrant current multiplier. It assists current divider to implement coefficient regulation of the programmable SI filter.(4) Using a difference bilinear SI integrator and a class AB grounded gate multiplier to implement a multifunction and adjustment SI biquadratic filter. It realized the LP, BP and HP functions. Besides, it can implement Butterworth filter, Chebyshev filter, Elliptic filter and the characteristics of the filter can be changed by simply varying the value of out-of-chip DC current sources.(5) Design the analog layout of the core cell and summarized the skills of SI layout.