TY - JOUR

T1 - Explicit design formulas for current-mode leap-frog OTA-C filters and 300 MHz CMOS seventh-order linear phase filter

AU - Sun, Y.

AU - Zhu, X.

AU - Moritz, J.

N1 - The defnitive article can be found at: http://www3.interscience.wiley.com/ Copyright Wiley. [Full text of this article is not available in the UHRA]

PY - 2010

Y1 - 2010

N2 - The leap-frog (LF) configuration is an important structure in analogue filter design. Voltage-mode LF OTA-C filters have recently been studied in the literature; however, general explicit formulas do not exist for current-mode LF OTA-C filters and there is also need for current-mode LF-based OTA-C structures for realization of arbitrary transmission zeros. Three current-mode OTA-C structures are presented, including the basic LF structure and LF filters with an input distributor or an output summer. They can realize all-pole characteristics and functions with arbitrary transmission zeros. Explicit design formulas are derived directly from these structures for the synthesis of, respectively, all-pole and arbitrary zero filter characteristics of up to the sixth order. The filter structures are regular and the design formulas are straightforward to use. As an illustrative example, a 300 MHz seventh-order linear phase low-pass filter with zeros is presented. The filter is implemented using a fully differential linear operational transconductance amplifier (OTA) based on a source degeneration topology. Simulations in a standard TSMC 0.18µm CMOS process with 2.5 V power supply have shown that the cutoff frequency of the filter ranges from 260 to 320 MHz, group delay ripple is about 4.5% over the whole tuning range, noise of the filter is 420nA/Hz, dynamic range is 66 dB and power consumption is 200 mW.

AB - The leap-frog (LF) configuration is an important structure in analogue filter design. Voltage-mode LF OTA-C filters have recently been studied in the literature; however, general explicit formulas do not exist for current-mode LF OTA-C filters and there is also need for current-mode LF-based OTA-C structures for realization of arbitrary transmission zeros. Three current-mode OTA-C structures are presented, including the basic LF structure and LF filters with an input distributor or an output summer. They can realize all-pole characteristics and functions with arbitrary transmission zeros. Explicit design formulas are derived directly from these structures for the synthesis of, respectively, all-pole and arbitrary zero filter characteristics of up to the sixth order. The filter structures are regular and the design formulas are straightforward to use. As an illustrative example, a 300 MHz seventh-order linear phase low-pass filter with zeros is presented. The filter is implemented using a fully differential linear operational transconductance amplifier (OTA) based on a source degeneration topology. Simulations in a standard TSMC 0.18µm CMOS process with 2.5 V power supply have shown that the cutoff frequency of the filter ranges from 260 to 320 MHz, group delay ripple is about 4.5% over the whole tuning range, noise of the filter is 420nA/Hz, dynamic range is 66 dB and power consumption is 200 mW.

U2 - 10.1002/cta.563

DO - 10.1002/cta.563

M3 - Article

SN - 0098-9886

VL - 38

SP - 367

EP - 382

JO - International Journal of Circuit Theory and Applications

JF - International Journal of Circuit Theory and Applications

IS - 4

ER -