RADIOENGINEERING, VOL. 18, NO. 1, APRIL 2009 83
A New Current Mode SIMO-Type Universal Biquad
Employing Multi-Output Current Conveyors (MOCCIIs)
Chunhua WANG, Yan ZHAO, Qiujing ZHANG, Sichun DU
School of Computer and Communication, Hunan University, Changsha, 410082, Hunan, P.R.China
wch1227164@sina.com, zhaoy1983@foxmail.com, clare014201@hotmail.com, d_sc@sina.com
Abstract. This study presents a new current-mode single-
input and multi-output (SIMO) type universal biquad cir-
cuit using second generation multi-output current convey-
ors (MOCCII) as the active components. The proposed
circuit employs three MOCCIIs, two grounded capacitors
and four grounded resistors, therefore offers electroning
tuning possibilities. It can simultaneously realize second
order low-pass, band-pass, high-pass, notch and all-pass
filters. The circuit is cascadable and has low sensitivities.
It provides independent control of ω
0
(natural angular
frequency) and Q (quality factor). The influences of
MOCCII parasitic elements have been analyzed and simu-
lated using PSPICE. Experimental results including fre-
quency responses of low-pass, high-pass, band-pass and
band-stop filters, as well as frequency responses of filters
with different ω
0
(keeping Q invariable) and different Q
(keeping ω
0
invariable) are shown to be in agreement with
theory.
Keywords
Current conveyor, current-mode circuit, filter.
1. Introduction
Second generation current conveyor (CCII) element
which has a single current output terminal is one of the
versatile active building blocks to construct continuous-
time universal and multipurpose filters, and many of these
filters have been reported in literature [1-5]. However,
there are two basic shortcomings of such filters: (1) They
can not provide feedforward and feedback currents at the
same time; (2) The circuits are rather complex. In order to
overcome such problems, some authors attempt to design
multipurpose and universal filters using other types of
active components [6-20]. On the other hand, a modified
CCII, so called multi-output current conveyor (MOCCII)
circuit was presented by Pal K [21]. It should be noted here
that, a MOCCII element can be realized by copying the
output current of an ordinary CCII using current mirroring
transistors for its positive output terminals, while its nega-
tive terminals can be designed by inverted current mirrors
which provide negative copies of the output current of the
basic CCII element. Various filters based on MOCCII have
already been presented in electronics literature [22-29].
In general, multi-purpose and universal filters can be
classified either as multi-input and single-output (MISO)
filter [23], [28], [30-33] or single-input and multi-output
(SIMO) filter [24-29]. The MISO current-mode filters have
rather simple structures. However, by the virtue of their
construction, they can not realize multiple outputs at the
same time, while MOCCII -SIMO type current-mode fil-
ters can realize low-pass (LP), band-pass (BP), high-pass
(HP), band-stop (BS) and all-pass (AP) filters simultane-
ously. Current-mode MOCCII-based SIMO filters in refer-
ences [24-25], [27] do not provide independent control of
natural angular frequency and the Q-factor.
In this paper, a novel current-mode SIMO second-or-
der filter based on MOCCII is proposed. It has only three
MOCCIIs and six RC elements, and it can realize LP, BP,
HP, BS and AP filters at the same time. The natural fre-
quency and quality factor can be tuned independently, and
all of the passive elements are grounded.
2. The Proposed Circuit
The circuit symbol of MOCCII is shown in Fig.1
where terminal Y behaves as a voltage signal input, termi-
nal X behaves as voltage track, z
1
~z
n
are non-inverting
outputs, and z
1-
~ z
m-
are inverting outputs. Its ideal port
characteristics can be expressed as:
,,0
yxy
vvi =
−−−+++
=−=−
zmzzznzz
iiiiii ......
2121
. (1)
Fig. 1. Circuit symbol of MOCCII.
The proposed SIMO current-mode second-order filter
is shown in Fig. 2. I
in
is input current and I
o1
~I
o5
are the
output currents. The filter is configured by three MOCCII
and two grounded capacitors and four grounded resistors.