Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
Contents lists available at ScienceDirect
International Journal of Electronics and
Communications (AEÜ)
journal homepage: www.elsevier.com/locate/aeue
Regular paper
Realization of DTMOS based CFTA and multiple input single output
biquadratic filter application
Muhammed Emin Basßak
Yildiz Technical University, Faculty of Naval Arch. and Maritime, Istanbul 34349, Turkey
a r t i c l e
i n f o
Article history:
Received 2 February 2019
Accepted 30 April 2019
Keywords:
CFTA
DTMOS
Filter
MISO type
Low voltage
Low power
a b s t r a c t
Analog filters can be found in everything from mobile phones to disk drives, from audio systems to power
supplies, from telecommunications to broadband internet connection. Analog filters can be formed from
a variety of active elements. In this study, the Dynamic Threshold Voltage MOSFET (DTMOS) based
Current Follower Transconductance Amplifier (CFTA) active element has been suggested and a multi
input single output (MISO) universal biquadratic filter has been obtained with this active element. The
proposed circuit operates with ±0.2 V supply voltages and consumes 140 mW power and electronically
tunable. All five filtering responses have been realized by selecting the different input signals. All simulations have been performed with LTSpice program using the Predictive Technology Model (PTM) 45 nm
Level 54 CMOS process parameters. Analysis of AC/DC, noise, Monte Carlo, temperature, total harmonic
distortion (THD) proves that the circuit operates in harmony with the theory. With Monte Carlo analysis,
it has been observed that the filter achieves stable output against both passive element and process
parameter tolerance. It is hoped that the proposed active element and the filter will be useful in ultralow voltage, low power, and low frequency analog signal applications.
Ó 2019 Elsevier GmbH. All rights reserved.
1. Introduction
Analog filters are used in many different systems such as modulation/demodulation, noise reduction, signal detection, sampling,
multiplexing, audio processing, transmission lines, and image processing. Even though many systems (even the signal processing
system) appear digitally, those systems may have one or more analog filters. Different filters are employed for different applications.
In the field of communication, band-pass filters are used in the frequency range of 0–20 kHz, while telephone center offices use highfrequency filters around a few hundred MHz for channel selection.
Although data acquisition systems prefer low-pass filters, system
power supplies use band-reject filters to suppress the 50 Hz or
60 Hz line frequencies. There are also systems that require allpass filters that cause a time delay by adding a linear phase shift
instead of filtering any frequency [1].
When creating filters for systems with frequencies higher than
1 MHz, resistor (R), inductor (L) and capacitor (C) are used. However, when the frequency is between 1 Hz and 1 MHz, a largevalue inductor is needed. Large-scale inductor is economically
expensive and occupies a large area for ICs. They emit more magnetic field than the other elements in the filter and contain much
E-mail address: mebasak@yildiz.edu.tr
https://doi.org/10.1016/j.aeue.2019.04.027
1434-8411/Ó 2019 Elsevier GmbH. All rights reserved.
more than parasitic parameters. In this case, active elements are
employed instead of coils [2–4].
In today’s world, it is very important to consume energy in the
most efficient way. It is not desirable that only large machines, but
also micro-products and nano-level electronic products have low
energy consumption. Power consumption is a critical parameter,
especially for medical electronic implant devices, handheld,
battery-powered devices and portable electronic devices. Since
most physiological signals are low frequencies, with low signal to
noise and low amplitude signals; low frequency filters are vital
for these signals. Research shows that power line interference on
a frequency of 50 Hz or 60 Hz is critical during physiological signal
recording. Power line noise can easily be collected from electrode
cables, electrical devices and the monitored patient. Especially in
mobile devices such as mobile phones and laptops are expected
to work with batteries for long periods without plugging in. Reducing power consumption allows the batteries of portable devices to
be used for longer periods. The most effective and easiest way to
reduce power consumption is to reduce the supply voltage. However, lowering the supply voltage causes problems such as signal
headroom or gate leakage in CMOS transistors. Although
switched-capacitor integrators [5], Operational Transconductance
Amplifiers-Capacitors (OTA-C) [6] are widely used for lowfrequency notch filters, they cannot easily be integrated into ICs
58
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
[7]. Due to these problems, the production of ultra-low supply and
ultra-low power devices becomes difficult. The DTMOS based transistor solves this problem.
In this work, DTMOS based CFTA and its multi input single output (MISO) filter has been suggested. The proposed DTMOS based
CFTA active element is appropriate for low-voltage and lowpower equipment, biomedical applications, audio systems and
analog signal processing applications.
In the literature, there are many studies [8–21] as a multi-input
voltage-mode biquadratic filter with different active elements. In
previous studies, the proposed circuits can operate at several kHz
or MHz levels, while the circuit proposed by us can operate at
low frequencies. Although all types of filters were obtained (allpass (AP), high-pass (HP), low-pass (LP), band-pass (BP), and notch
(NH)), there are one or more deficiencies in the previously reported
circuits. Some of them have low input impedance [14,17] or the
resonance angular frequency and quality factor cannot be controlled in orthogonally [8,9,14–16]. Some of them [9,11,16,19–
21] use too many active or passive components. The previously
proposed circuits operate at high frequencies at several hundred
kHz to MHz levels and do not operate at low frequencies. The
detailed specifications of the filters and their comparison with
the proposed filter are given in Table 4 in Section 4.
The CFTA was firstly introduced in 2009 as a simplified version
of the Current Differencing Transconductance Amplifier (CDTA)
[22]. After it was introduced, different filters, oscillators and
inductance simulators were presented [23–27]. The most important advantages of CFTAs compared to conventional op-amps are,
the greater the linearity and the greater the bandwidth. The important properties of the proposed active circuit and filter are given
below:
i. The circuit has a high input impedance.
ii. Operates with ultra-low supply voltage and ultra-low power
consumption.
iii. It has electronically tunable and high transconductance.
iv. Only one active device is used to construct the MISO biquadratic filter
v. Designed filter can be used for low-frequency applications.
vi. With the same circuit configuration, low-pass, high pass,
band-pass, notch and all-pass filters can be obtained.
The rest of this paper is organized as follows. The second section
presents DTMOS transistors briefly and the DTMOS based Current
Follower Transconductance Amplifier. The characteristic matrix,
equivalent circuit and CMOS realization of the active device is
given in this section. New multi input single output biquadratic filter topology and its transfer function is presented in Section 3. All
the simulation results and the comparison table of the previously
reported voltage mode biquadratic MISO filters are given in
Section 4. The last section is the conclusion.
2. DTMOS based current follower transconductance amplifier
The Dynamic Threshold Voltage MOSFET (DTMOS) was firstly
proposed by Assederaghi et al. [28,29] in 1994 on a silicon on insulator (SOI) process. Their aim was to extend the lower limit of the
power supply to extremely low voltages (0.2 V and below). They
tied the body and gate of the MOSFET to operate the DTMOS
[29]. Fig. 1 shows the connection of the DTMOS transistor and
the circuit symbol.
The DTMOS transistor can operate high success with low supply
voltages, if the forward body polarity is done correctly depending
on the conditions. The DTMOS transistor is obtained as a result
of the MOS gate being connected to the bulk of the transistor.
Fig. 1. DTMOS transistor connection and DTMOS display [30].
The body is recognized as an element operating according to the
principle of functioning as low voltage in case of forward polarity
of the source function. In MOS technology, the mathematical
expression of the level of the transistor’s threshold voltage is due
to the body varying depending on the source voltage. Accordingly,
a DTMOS body can be perceived as a member having a dynamic
characteristic since it is connected to the gate body with the source
voltage change.
In addition, because it exhibits a higher transconductance than
a normal MOS transistor, it is a useful element for today’s low
power consumption, low voltage analog circuits by delivering
higher currents at lower supply voltages. It is proposed in the literature firstly because it provides power saving in low supply voltages in digital circuits and low leakage current value at the same
time [28,31]. On the other hand, it also improves the performance
of high transconductance circuits in low supply voltage analog circuits and is also suitable for low supply voltage analog circuit
designs [7,28–30,32]. Another feature of this transistor is that the
DTMOS transistor exhibits a subthreshold oscillation very close
to the ideal when operated with subthreshold voltage. Thanks to
this characteristic, which has a subthreshold operation compared
to a normal MOS transistor, the DTMOS transistor appears to be
a suitable element for very low power consumption circuit designs
operating under the threshold.
Under certain constraints, the DTMOS technique can be applied
to the PMOS transistors inexpensive standard CMOS manufacturing process without requiring extra production steps [28]. If nwell process technology is used, only the body terminal of the
PMOS transistor can be obtained. In order to obtain the body terminals of both NMOS and PMOS transistors, the more expensive
triple-well application must be performed simultaneously. With
the extra terminal to be obtained, it can open up new possibilities
and different applications in analog circuit design [30,33].
The schematic symbol and equivalent circuit of Current Follower Transconductance Amplifier are shown in Fig. 2(a) and (b),
respectively.
The operation of CFTA is defined by following matrix equation:
2
vF
6 i
6 Z
6
4 iX þ
iX
3
2
0
0
7 6a
0
7 6
7¼6
5 4 0 þgm
0
gm
0 0
32
iF
6
0 07
76 vZ
76
5
0 0 4 vX þ
0 0
vX
3
7
7
7
5
ð1Þ
The inner structure of DTMOS based CFTA is shown in Fig. 3. The
CFTA structure of [26] was used to construct the DTMOS based
CFTA circuit, while the dimensions in the proposed circuit were
modified to match the DTMOS transistors. The threshold voltage
of the DTMOS transistor is utilizing the relation in Eq. (2);
VTH ¼ VTH0 þ c
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffi
/0 þ VSB /0
ð2Þ
where VTH0 is the zero bias threshold voltage, c is body effect coefficient, /0 is the total surface band bending, and VSB is the potential
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
I2
iF
F
F
I3
X-
CFTA
X+
Z
iXiX+
iF
Vx-
59
ix
gmvz
ix
gmvz
X+
X-
Vx+
iz iF
Z
iZ
Fig. 2. (a) Symbol and (b) equivalent circuit of CFTA.
Fig. 3. The structure of the DTMOS based CFTA circuit.
difference from the source to bulk. The DTMOS transistors have a
low threshold voltage at the VGS = VDD and high threshold voltage
at zero bias. The drain current of the DTMOS transistor is given in
Eq. (3) and the transconductance (gm) is described in Eq. (4).
ID ¼ IS
W
VGS VTH
VDS
exp q
1 exp q
L
nkT
kT
gm ¼ q
ID
nkT
ð3Þ
ð4Þ
The transconductance change of the proposed DTMOS - based
CFTA circuit is given according to the changing current values (I2
and I3). As can be seen from Figs. 4 and 5, gm values can be controlled electronically with I2 and I3 currents. The transconductance
variance of the proposed active element for different I3 currents at
fixed I1 = 20 mA, I2 = 150 mA and variation of I3 (0–150 mA) is shown
in Fig. 4. The range of transconductance values of fixed
I1 = I2 = 50 mA and variables of I3 (0–150 mA) is shown in Fig. 5.
The transconductance value is 4.06 mS for the I3 current was
150 mA, while the transconductance was 2.05 mS when the I3 current was zero. Since transconductance change is provided electronically with I2 and I3 currents, the proposed circuit has an electronic
tuning feature. The DC transfer characteristics of the transconductance stage of the terminal voltage are shown in Fig. 6. The frequency response of the current gain IZ/IF is depicted in Fig. 7. The
current gain of IZ/IF is 1 and current transfer bandwidth is
99.24 MHz.
3. Multi input single output biquadratic filter
A universal biquadratic multi-input single output filter is proposed to demonstrate the applicability of the proposed DTMOS-
Fig. 4. Transconductance of the proposed CFTA (I1 = 20 mA and I2 = 150 mA).
based CFTA active element. The connection of the filter is shown
in Fig. 8.
The non-ideal and ideal transfer functions can be written with
the Eqs. (5) and (6) of the system which the output node is Vx+,
respectively. All the transfer functions of the universal filter are
given in Table 1.
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
60
Fig. 7. Frequency response of the current gain (IZ/IF).
Fig. 5. Transconductance of the proposed CFTA (I1 = I2 = 50 mA).
Fig. 8. The proposed Multi Input Single Output filter.
Table 1
Transfer functions of the obtained universal MISO biquadratic filter.
Filters
Input voltages
Transfer functions
All-pass
V1 = 1, V2 = V3 = 1
VAP
Vin
¼
C1 C2 R1 R2 R3 s2 þ C2 R1 R2 s þ gm R1 R3
DðsÞ
Low-pass
V2 = 1, V1 = V3 = 0
VLP
Vin
¼
gm R 1 R 3
DðsÞ
High-pass
V1 = 1, V2 = V3 = 0
VHP
Vin
VBP
Vin
¼
C1 C2 R1 R2 R3 s2
DðsÞ
C2 R 1 R 2 s
DðsÞ
Band-pass
V1 = V2 = 0, V3 = 1
Notch
V1 = 1, V2 = 1, V3 = 0
¼
Vnotch
Vin
¼
C1 C2 R1 R2 R3 s2 þ gm R1 R3
DðsÞ
Fig. 6. DC response of proposed DTMOS based CFTA.
Vx þ ¼
1 C2
þ
sC2
R1
þ
agm V2
agm
R1
þ
sC2
R3
sC2 V3
þ agm
sC2
sC2
2
2
2
2
R2 s C1 C2 þ R1 þ R1 þ R3
R3 s C1 C2 þ sC
þ aRg1m þ sC
R1
R3
Vx þ
The pole frequency (x0 ) and quality factor ( ) is given by Eqs.
(8) and (9), respectively;
s2 C1 C2 V1
s2 C
C1 C2 R1 R2 R3 s2 V1 gm R1 R3 V2 C2 R1 R2 sV3
¼
þ
DðsÞ
DðsÞ
DðsÞ
DðsÞ ¼ C1 C2 R1 R2 R3 s2 þ C2 R1 R2 s þ C2 R2 R3 s þ gm R2 R3
ð5Þ
x0 ¼
ð6Þ
Q ¼
ð7Þ
The transfer functions of all-pass, low-pass, high-pass, bandpass, and notch filters according to V1, V2 and V3 voltage values
in the ideal transfer function are summarized in Table 1.
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
gm
C1 C2 R1
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
gm C1 R1
R3
C2
R1 þ R 3
ð8Þ
ð9Þ
The pole frequency and the quality factor can be electronically
controlled through gm. The quality factor can be controlled without
affecting the pole frequency by R3 resistor. The non-ideal pole frequency (x0 ) and quality factor ( ) is given by Eqs. (10) and (11),
respectively;
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
gm a
x0 ¼
C1 C2 R1
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
gm aC1 R1
R3
Q ¼
C2
R1 þ R3
61
ð10Þ
ð11Þ
4. Simulation results
In order to demonstrate the performances of the proposed
active element and MISO biquadratic filter, LTSpice simulations
were carried out. The proposed active circuit and its filter applications are all simulated by LTSpice using PTM 45 nm Level 54 CMOS
process model parameters. The proposed filter shown in Fig. 8 is
simulated with the following passive element values:
R1 = R2 = R3 = 1 kO and C1 = 4 mF and C2 = 1 mF. Bias currents are
I1 = 20 mA, I2 = 50 mA, and I3 = 50 mA. Thus, the filters in Figs. 9
and 10 are obtained. Without changing the resistors, capacitors
C1 = 4 nF and C2 = 1 nF value is used to obtain Figs. 11 and 12.
Amplitude curves of all the filters in Figs. 9–12 are obtained by
using supply voltages VDD = VSS = 0.2 V. The dimensions of the
CMOS transistors used in the CFTA implementation are presented
in Table 2. Figs. 9 and 11 shows the HP, LP, BP and NH outputs,
while Figs. 10 and 12 are all-pass amplitude and phase curves of
low and high frequencies. The change of the center frequency of
the notch filter according to the changing I3 bias current is shown
in Fig. 13. The following passive element values are used:
R1 = R2 = R3 = 1 kO and C1 = 400 pF and C2 = 100 pF and bias currents are I1 = 70 mA, and I2 = 80 mA of ±0.2 V supply voltages. As
seen from the figure, the center frequency of the filter varies
between 814 kHz and 1.22 MHz according to three different I3 currents ranging from 0 to 100 mA. It has been shown that the proposed filter is electronically tunable and can operate at high
frequencies. In Fig. 14, the transient analysis of the central frequency of 89 kHz band-pass filter, which is the gain curve is shown
in Fig. 11, is performed. Due to the gain of 6 dB of the band-pass
filter, the output signal is reduced by half. Figs. 15 and 16 show the
transient analysis of the all-pass filter of the same circuit. There is a
shift between the input and output signals due to the change in
phase at 89 kHz frequency. In Fig. 16, the input and output signals
Fig. 10. Amplitude and phase curves of all-pass filter (low frequencies).
Fig. 11. Amplitude curves of filters (BP and notch filter center frequency is
approximately 89 kHz).
Fig. 9. Amplitude curves of filters (BP and notch filter center frequency is 89 Hz).
of the all-pass filter overlap because the phase difference at
10 MHz is 360°.
When the input and output noise performance of the circuit
p
were examined, the input noise was found to be 420 nV Hz for
p
50 Hz frequencies and 41.7 nV Hz for 89 kHz. The output noise
p
p
was found to be 438.32 nV Hz for 50 Hz and 18.20 nV Hz for
89 kHz. The input and output noise is shown in Fig. 17.
According to the tolerance of passive elements and process
parameters of the proposed notch filter, central frequency, and
quality factor are investigated by the Monte Carlo analysis. Monte
Carlo analysis was performed to demonstrate the central frequency
variation of the proposed notch filter, depending on all resistors
and capacitors tolerance. Monte Carlo analysis was performed for
10% mismatches in resistors and capacitor values with Gaussian
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
62
Fig. 12. Amplitude and phase curves of all-pass filter (high frequencies).
Fig. 14. Transient analyses of band-pass filter at 89 kHz.
Table 2
MOSFET dimensions of DTMOS based CFTA.
Transistor
Width (mm)
Length (nm)
M1 – M7, M9, M10,
M8
M11, M12
M13 – M18
M19 – M22
M23, M24
180
270
600
200
100
150
90
90
90
90
90
90
Fig. 15. Transient analyses of all-pass filter at 89 kHz.
Fig. 13. Change of center frequency of notch filter with I3 bias current.
distribution for 500 runs. Resistors and capacitor values are respectively R1 = R2 = R3 = 1 kO; C1 = 5 mF and C2 = 2.5 mF. The resulting
center frequency and quality factor changes are shown in Figs. 18
and 19, respectively. It is seen that center frequency changes
between 44 Hz and 69 Hz according to the Gaussian distribution.
The average value is 50.99 Hz, and the median value is 50.46 Hz,
which is very close to the expected 50 Hz center frequency. The
quality factor varies from 0.64 to 1.02 as seen Fig. 19. It can be said
that the design is sufficiently stable against the passive element
tolerance.
Monte Carlo analysis was performed to determine the center
frequency and bandwidth changes of the notch filter according to
gate-oxide thickness (tOX), zero-bias threshold voltage (VTH0)
parameters of the values supplied by PTM and transistor width
(W) changes. In the analysis of the parameters, Gaussian distribution was applied for 10% mismatch for 1000 runs were done. In
these conditions, the change of the center frequency is indicated
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
Fig. 16. Transient analyses of all-pass filter at 10 MHz.
63
Fig. 18. Center frequency (f0) distribution of notch filter depending on resistors and
capacitors tolerance.
Fig. 17. Input and output noise of the proposed filter.
in Fig. 20. It is seen that center frequency changes between 42 Hz
and 62 Hz. According to simulations, the average value of the center frequency is 49.87 Hz, which is very close to 50 Hz center frequency. Corresponding to the Monte Carlo simulation, the
proposed filter has low sensitivity to transistor dimensions (change
in width) and deviation of process parameters tOX and VTH0 (see
Fig. 21).
Total harmonic distortion values obtained from the sinusoidal
input signal at the 89 kHz frequency of the proposed band-pass filter are shown in Fig. 22. The total harmonic distortion of the proposed filter was less than 4% for input not exceeding 140 mV peak
to peak voltage. These results show that the percentage of THD is
within acceptable limits. It is simulated for different temperature
values ranging from 25 °C to 75 °C to examine the effect of temperature changes on the performance of the proposed MISO filter.
Fig. 19. The quality factor distribution of the notch filter depending on resistors and
capacitors tolerance.
The results are shown below in Fig. 23. When the temperature
reaches 75 °C, a slight decrease is noticed in the notch filter
amplitude.
To make a performance comparison with previous studies, Figure of Merit (FOM) is defined numerically. Definition of FOM is:
FOM ¼
106 ðlm2 V lWÞ
Areaðlm2 Þ SVðVÞ PðlWÞ N
ð12Þ
where 106 is the constant which provide the dimensionless FOM;
Area (lm2 ) is approximately layout area of the circuit in which
sums of products of the lengths and widths of each MOS transistor
used; SV (V) is supply voltages; P (lW) is total power dissipation,
64
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
Fig. 20. The center frequency variation of the proposed notch filter depending on
the process parameters (tOX & VTH0) and transistor widths (W).
Fig. 22. THD variations of the proposed biquadratic band-pass filter at 89 kHz
frequency.
Temperature rises
Fig. 23. Notch filter center frequency change with temperature.
Fig. 21. The bandwidth distribution of the notch filter depending on the process
parameters (tOX & VTH0) and transistor widths (W).
and N is the number of active devices. The calculated FOM shows its
superiority as its value is high. FOM results of the other studies and
the proposed circuit are compared in Table 3.
There are many studies in the literature as a multi input single
output voltage-mode biquadratic filters with different active elements. Five types of standard filter functions can be obtained by
selecting different input voltage terminals in these circuits. However, these circuits have one or more of the disadvantages shown
below. Table 4 shows the comparison of the previously proposed
MISO filters with the voltage mode MISO filter realized with the
DTMOS based CFTA active element. The comparison is constructed
according to the following specifications.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
Active element
Number of active elements
Number of passive elements (R + C)
Electronically tunable (controllability)
High input impedances
All filter functions (All-pass, band-pass, band-reject, highpass, low-pass)
Power supplies
Power consumptions
Can be used in the low frequencies applications
Orthogonal tuning capability for the resonance angular frequency and quality factor
M.E. Basßak / Int. J. Electron. Commun. (AEÜ) 106 (2019) 57–66
65
Table 3
Comparison between the proposed MISO filter and some previously reported MISO filters.
*
Filters
Area* (lm2 )
Supply voltage (V)
P (lW)
N (number)
FOM
This work
[19]
[20]
[21](1.cir)
[21](2.cir)
[13]
[34]
476.1
668.44
200
303.75
303.75
47.45
122.5
0.4
3
3.30
2.5
2.5
3.6
3.0
140
3470
1240
4266
4261
440
970
1
3
5
3
3
1
2
37.50
0.0479
0.244
0.102
0.103
13.30
1.4026
The total layout areas are calculated with given Width and Length of the transistors of the relevant paper.
Table 4
Comparison of the previously reported voltage mode biquadratic MISO filters.
Filters
This work
[8]
[9]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21](1.cir)
[21](2.cir)
[11]
[12]
[13]
[34]
Year
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
2001
2003
2003
2004
2007
2007
2010
2010
2012
2012
2012
2017
2017
2018
2011
CFTA
CCII+
OTA + CCII
DDCC
CCIIDDCC
DVCC
CFTA
DVCC
OTA + CCII
DVCC
DVCC + DDCC
DDCC+
VDDDA
VDTA
VDBA
1
3
3
2
2
3
2
1
3
5
3
3
3
2
1
2
3R + 2C
2R + 2C
2C
2R + 2C
2R + 2C
2R + 2C
4R + 2C
2R + 2C
3R + 2C
2C
4R + 2C
4R + 2C
5R + 2C
2C
1R + 2C
2C
Yes
No
No
No
No
No
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
±0.2 V
NA*
NA*
±3.3 V
NA*
±1.65 V
±1.25 V
±3V
±1.5 V
±1.65 V
±1.25 V
±1.25 V
±0.9 V
±5 V
±1.8 V
±1.5 V
140 mW
NA*
NA*
NA*
NA*
NA*
NA*
NA*
3.47 mW
1.24 mW
4.26 mW
4.26 mW
NA*
NA*
0.44 mW
0.97 mW
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
37.50
NA*
NA*
NA*
NA*
NA*
NA*
NA*
0.0479
0.244
0.102
0.103
NA*
NA*
13.30
1.402
NA*: Not Available.
(k) Calculated Figure of Merit (FOM) value
5. Conclusions
In this study, the DTMOS based CFTA active element was proposed. The active element has a high input impedance and operates with ultra-low supply voltage and ultra-low power
consumption. It has electronically tunable and high transconductance. MISO universal voltage mode biquadratic filter was designed
to show the utility of the proposed active element. The proposed
MISO universal voltage mode biquadratic filter consisted only
one DTMOS based CFTA and five passive components. With the
same circuit configuration, low-pass, high pass, band-pass, notch
and all-pass filters can be obtained. In order to demonstrate the
performances of the proposed circuits, the simulation performed
using the Predictive Technology Model (PTM) 45 nm Level 54
CMOS process parameters. AC/DC, Monte Carlo, noise, temperature, and THD analyses were performed. The main feature of the
filter is that it can operate at low frequencies with low-voltage
and low-power dissipation by using a single active element. With
Monte Carlo analysis, it has been observed that the filter achieves
stable output against both passive elements and process parameter
tolerance. This paper has been focused on new possibilities of
DTMOS use. It is hoped that the proposed active element and the
filter will be useful in many analog signal applications, especially
in applications that require low frequency and low power
consumption.
Appendix A. Supplementary material
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.aeue.2019.04.027.
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