25-10-2012, 03:22 PM
A Novel CM-Universal Filter Employing Single CDTA
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Abstract—
A new universal filter employing single
current differencing transconductance
amplifier(CDTA), using current mode approach
which provides high pass(HP),band pass(BP),low
pass(LP) responses simultaneously, has been
presented. The current outputs of lowpass(LP) and
bandpass(BP) types for driving independent loads
and single highpass(HP) current output, flowing
through one of working capacitors. The circuit
employes one CDTA, two capacitors and one
resistors. It uses a minimum number of passive and
active components, which provides low active and
passive sensitivities. PSPICE simulation results
which utilizes the cmos transistor based CDTA
model, are enclosed.
INTRODUCTION
Current differencing transconductance amplifier
(CDTA) is used especially for current mode analog
signal processing[1].It has been introduced [10]-
[12] for the synthesis of active filters.A variety of
applications of Current differencing
transconductance amplifier (CDTA) can be found in
various literature[3].The active filters in CM have
wider band width,simpler circuitry,greater
linearity,wider dynamic range and lower power
consumption as compared to their voltage mode
counterparts[4]-[9].The circuits reported so far
suffer from the drawbacks of employing either
excessive number of components[2][3] or need to
change the circuit topology to realize different
filtering responses .A number of papers deal with
the design of 2nd order CDTA based filter,most of
them contains[2][3] two CDTAs.CDTA can be
thought as a combination of a Current differencing
unit followed by a dual-output operational
transconductance amplifier,DO-OTA.OTA is a
voltage-controlled current source device and can be
described by:
CONCLUSION
A novel 2nd order CM-universal filter using a single
CDTA is described in this paper.The circuit besides
using minimum number of active and passive
components can simultaneously provides three basic
filtering functions viz LP,HP and BP. o w and B Are
orthogonally tunable. PSPICE simulation of this
circuit confirms the theoretical conclusions.