CMOS Analog Filter Design

Summary

Shown above is a 5th order continuous-time Gm-Opamp-C filter intended to test algorithms for the digital adaptation of analog filters. All 5 poles and zeros are digitally programmable. An orthonormal ladder structure is used to optimize dynamic range scaling over a wide range of operating conditions. Constant capacitances are combined with digitally controlled transconductances to provide programmability.

Results Summary

	5th order orthonormal ladder filter
	Technology: 0.25 um digital CMOS
	Supply Voltage: 2.5 V
	Total Area: 2.5 mm x 1.7 mm
	Active Area: 1.36 mm x 0.53 mm
	Nominal Power Dissipation: 130 mW
	Max. Signal Bandwidth: 100 MHz
	9-bit digitally programmable poles and zeros:

Future work

Filters for high speed communication applications are needed for equalization, echo cancellation, and crosstalk cancellation. Traditional filter architectures and circuit topologies may not be suitable for the GHz range. Investigations are required at the system, circuit, and device levels.

Reference

A. Chan Carusone and D. A. Johns, "A 5th Order Gm-C Filer in 0.25 um CMOS with Digitally Programmable Poles & Zeroes," IEEE Int. Symp. Circuits and Syst., May 2002. [PDF Format], [PDF Format, Slides]