Int. J. Electron. Commun. (AEÜ) 62 (2008) 316–319
Hua-Pin Chen∗, Sung-Shiou Shen, Jenn-Pyng Wang
Department of Electronic Engineering, De-Lin Institute of Technology, Taiwan, ROC
Received 30 January 2007; accepted 29 April 2007
A novel electronically tunable versatile voltage-mode universal biquad filter by using two single-output-operational
transconductance amplifiers (OTAs), one differential difference current conveyor (DDCC) and two capacitors is proposed.
The proposed circuit, which can be used as either a four-input single-output universal filter or a single-input three-output
multifunction filter with the same topology. Besides, the new circuit offers the following advantageous features: realization
of all the non-inverting and inverting biquadratic filter signals from the same configuration, no need to employ inverting-type
input signals, no need to component-matching conditions and low passive sensitivity performance.
? 2007 Elsevier GmbH. All rights reserved.
Keywords: Active filters; Voltage-mode circuits; Current conveyers
Many current-mode and voltage-mode universal bi-
quadratic filter circuits employing operational transconduc-
tance amplifiers (OTAs) had been reported in the literature
[1–7]. These designs of OTA-C filter circuits require no
resistors. Therefore, they are suitable for monolithic inte-
gration than the other current conveyors. Moreover, an OTA
provides a highly linear electronic tunability and a wide
tunable range of its transconductance gain. Therefore, the
filters based on OTAs are the attention for many researches.
Recently, the use of differential difference current convey-
ors (DDCCs) in filters design has received considerable
attention because it can utilize the addition and subtraction
operators at the port X terminal [9–15]. In 2003, Horng
 proposed a high-input impedance voltage-mode univer-
sal biquadratic filter with three inputs and single output
∗Corresponding author. Tel.: +886222733567x388.
E-mail addresses: firstname.lastname@example.org (H.-P. Chen), email@example.com
(S.-S. Shen), firstname.lastname@example.org (J.-P. Wang).
1434-8411/$-see front matter ? 2007 Elsevier GmbH. All rights reserved.
employing two multiple current output OTAs, one plus-
type second-generation current conveyor and two floating
capacitors. It needed an inverting-type voltage input signal
to realize the allpass (AP) filter response. In 2005, Nisar
et al.  proposed a versatile voltage-mode universal filter
with three inputs and three outputs employing three current
feedback amplifiers, three resistors and two capacitors. The
proposed circuit is capable of implementing as many as 18
filtering functions, but needed component-matching con-
ditions to realize some filtering functions. Recently, Shah
and Malik  proposed a voltage-mode bandstop (BS),
bandpass (BP) and lowpass (LP) filters employing two four-
terminal floating nullors, one OTA, two grounded capacitors
and two resistors. However, this circuit needs employing
external passive resistors to realize the same voltage-mode
multifunction filter. In this paper, the authors present a new
versatile universal voltage-mode filter with four inputs and
three outputs employing two OTAs, one DDCC and two ca-
pacitors. The proposed configuration can act as a multifunc-
tion voltage-mode filter with single input and three outputs,
and can simultaneously realize voltage-mode LP, BP and BS
filter signals from the three output terminals, respectively,