Multifunction Voltage-Mode Filter Using Single Voltage Differencing Differential Difference Amplifier
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Multifunction Voltage-Mode Filter Using Single Voltage Differencing Differential Difference Amplifier
Amornchai Chaichana 0
Surasak Sangyaem 0
Winai Jaikla 0
0 Department of Engineering Education, Faculty of Industrial Education, King Mongkut's Institute of Technology Ladkrabang , Thailand
In this paper, a voltage mode multifunction filter based on single voltage differencing differential difference amplifier (VDDDA) is presented. The proposed filter with three input voltages and single output voltage is constructed with single VDDDA, two capacitors and two resistors. Its quality factor can be adjusted without affecting natural frequency. Also, the natural frequency can be electronically tuned via adjusting of bias current. The filter can offer five output responses, high-pas (HP), band-pass (BP), band-reject (BR), low-pass (LP) and all-ass (AP) functions in the same circuit topology. The output response can be selected by choosing the suitable input voltage without the component matching condition and the requirement of additional double gain voltage amplifier. PSpice simulation results to confirm an operation of the proposed filter correspond to the theory.
1 Introduction
In analog image processing system, the filter is the main
circuit that is used to separate the desired signal from
undesired ones. Especially, the versatile filter called as
multifunction filter has been gained significant attention
and has become an interesting research topic. Because the
multifunction filter can provide several filter responses in
the same circuit topology [1]. The multiple inputs single
output (MISO) multifunction filter belongs to popular
filter structures. An important feature of this structure is
the generation of several output transfer functions, i.e.,
high-pas (HP), band-pass (BP), band-reject (BR),
lowpass (LP) and all-ass (AP) with single output node while
the output response can be selected by suitable input
signals. The popular way to select the input signal is to
use the digital or electronic switch which is easily
controlled by microcomputer or microcontroller. So, the
MISO filter structure should not require the double input
signal to avoid the addition al amplifier.
The voltage differencing differential difference
amplifier (VDDDA) is the interesting active building
block. This active device consists of three subtraction
/addition voltage signal terminals with electronically
tunable transconductance. With this feature, it can be
found the VDDDA based analog circuits in the literature
for examples, first order voltage mode filter [2],
sinusoidal oscillator [2], inductance simulator [4], single
input multiple output voltage mode filter [5]-[6], multiple
input multiple output voltage mode filter [7] etc.
Recently, the VDDDA based three inputs single output
voltage mode multifunction filter [8] was published. This
filter is attractive because it is minimum number of active
element consisting of single VDDDA, single resistor and
two capacitors. The natural frequency and quality factor
can be electronically controlled. However, the inverting
double gain voltage amplifier is required for getting the
all-pass response.
In this paper, a voltage mode multifunction filter
based on single voltage differencing differential
difference amplifier (VDDDA) is proposed. The filter
with three input voltages and single output voltage is
constructed with single VDDDA, two capacitors and two
resistors. Its quality factor can be adjusted without
affecting natural frequency. Also, the natural frequency
can be electronically tuned via adjusting of bias current.
The filter can offer five output responses, high-pas (HP),
band-pass (BP), band-reject (BR), low-pass (LP) and
allass (AP) functions in the same circuit topology. The
output response can be selected by choosing the suitable
input voltage without the component matching condition
and the requirement of additional double gain voltage
amplifier. PSpice simulation results to confirm an
operation of the proposed filter correspond to the theory.
2 Circuit configuration and analysis of
the proposed filter
2.1 VDDDA
In order to understand the proposed filter, the brief details
of the active building block, VDDDA are given in this
section. The symbolic representation of VDDDA is
shown in Fig. 1(a). It has five input voltage terminals,
called as V+, V-, Z, P and N ports. The Z port is also the
output current terminal and the W port is the output
voltage. Ideally, the impedance at V+, V-, Z, P and N
ports are assumed to be infinite while the impedance at W
port exhibits low. The equivalent circuit is illustrated in
Figure 1(b). In this design, the VDDDA is constructed
from CMOS technology as illustrated in Figure 1(c). The
idealization of VDDDA’s parameters implies that
“where μ is the mobility of the carrier for NMOS
transistors, M15 and M16 in Fig. 1(c), Cox is the gate
oxide capacitance per unit area, W and L are the channel
width and channel length, (...truncated)