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©2009 Old City Publishing, Inc.Published by license under the OCP Science imprint,
a member of the Old City Publishing Group
J. of Active and Passive Electronic Devices, Vol. 4, pp. 35–53Reprints available directly from the publisherPhotocopying permitted by license only
35
*Corresponding author: [email protected]
Realization of CMOS Current Controlled Current Conveyor Transconductance Amplifier
(CCCCTA) and Its Applications
Montree Siripruchyanun1, phaMorn Silapan2 and Winai Jaikla3
1Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut’s University of Technology North Bangkok, THAILAND. E-mail: [email protected]
2Electric and Industrial Program, Faculty of Industrial Technology, Uttaradit Rajabhat University, THAILAND
3Electric and Electronic Program, Faculty of Industrial Technology, Suan Sunandha Rajabhat University, THAILAND. E-mail: [email protected]
This article presents a basic building block for analog signal processing, namely current controlled current conveyor transconductance amplifier (CCCCTA). Its parasitic resistance at current input port can be controlled by an input bias current. It is very suitable to use in either current-mode or voltage-mode signal processing systems. The proposed element was realized in a CMOS technology and was examined the performances through PSPICE simulations. They display usabilities of the new active element, where the maximum bandwidth is 107.34 MHz. The supply voltages can be as low as ±1.5 V and maximum power consumption is 899 µW. The CCCCTA per-forms tuning over a wide current range. In addition, some examples as a voltage and current-mode universal biquad filter and a grounded inductance simulator are included. They occupy only single CCCCTA.
Keywords: CMOS, CCCCTA, Current-mode, Voltage-mode, Filter, Oscillator, Inductance simulator.
1 InTROduCTIOn
There has been much effort to reduce the supply voltage of electronic circuits in last decade. This is due to the command for portable and battery-powered equipment. Since a low-voltage operating circuit becomes necessary, the cur-rent–mode technique is ideally suited for this purpose more than the voltage-
36 M. Siripruchyanun et al.
mode one. Consequently, there is a growing interest in synthesizing the current-mode circuits because of more their potential advantages such as larger dynamic range, higher signal bandwidth, greater linearity, simpler circuitry and lower power consumption [1–2]. Many active elements able to function in current-mode such as OTA, current conveyor and current differencing buff-ered amplifier (CDBA), have been introduced to response these demands.
Recently, a reported 5-terminals active element, namely current conveyor transconductance amplifier (CCTA) [3], seems to be a versatile component in the realization of a class of analog signal processing circuits, especially analog frequency filters [3–5]. It is supposed for usage mostly in current-mode circuits, but it is also choice in case of voltage mode and/or hybrid (voltage-current) circuits (e.g. V/I converters). In addition, it can also be adjusted the output cur-rent gain. However, from our investigations, there are seen that the CCTA can not be controlled by the parasitic resistance at input port so when it is used in some circuits, it must unavoidably require some external passive components, especially the resistors. This makes it not appropriate for IC implementation due to occupying more chip area. In addition, the mentioned CCTA has the third-generation current conveyor (CCIII) as an input stage which has flexibility for applications less than a second-generation current conveyor (CCII).
The purpose of this paper is to design and synthesize a modified-version CCTA, which is newly named current controlled current conveyor transcon-ductance amplifier (CCCCTA). The parasitic resistance at current input port can be controlled by an input bias current, and then it does not need a resistor in practical applications. Even it can be implemented by employing second-generation current controlled current conveyor (CCCII) and OTA, it would be more very convenient and useful if the CCCCTA is realized in monolithic chip. Some example applications as voltage and current-mode universal filters, grounded inductance simulator and oscillator are comprised. They confirm that only single CCCCTA is employed for each application.
2 CIRCuIT COnfIguRATIOn
2.1 Basic Concept of CCCCTACCCCTA properties are similar to the conventional CCTA, except that the CCCCTA has finite input resistance R
x at the x input terminal. This parasitic
resistance can be controlled by the bias current IB1
as shown in the following equation
IVII
R
g
y
x
z
o
x
m
=
±
0 0 0 01 0 0
1 0 0 00 0 0
IIVVV
x
y
z
o
, (1)
realization of cMoS ccccta and itS applicationS 37
where R
Ix
n B
=1
8 1β, (2)
and
g Im n B= β 2 . (3)
gm
is the transconductance of the CCCCTA, β µn n oxC W L= ( )/ is the physi-cal parameter of MOS transistor and V
T is the thermal voltage. The symbol
and the equivalent circuit of the CCCCTA are illustrated in Figs. 1(a) and (b), respectively.
2.2 A Second generation Current Controlled Current Conveyor (CCCII)Fig. 2 displays a class AB translinear loop, which is used as input section. By straightforward analysis, we will obtain the parasitic resistance at input terminal as
Rg g
I
I g g
g
g
g
ginm m
B
in m m
m
m
m
m
=+( )
−+( )
−
1
2 4
1
2 4
2
1
4
3
. (4)
From Eq. (4) if g g g g gm m m m m1 3 2 4= = = and , we will get
Rg I
inm n B
= =1
2
1
8 1β. (5)
Based on the use of the finite input resistance input stage of Fig. 2, the second generation current controlled current conveyor can be shown in Fig. 3. When V
y is grounded, the output current I
z can be expressed as
I Iz x= +α ε, (6)
FIGURE 1CCCCTA (a) Symbol (b) Equivalent circuit.
1BI
y
x z
oCCCCTA
yi
xi zioi±
2BI
yV
xV zVoV
(a)
1y
x
o
xixi
m Zg V±
xR z
(b)
38 M. Siripruchyanun et al.
where α and ε are current gain and error terms, respectively. By straightfor-ward analysis of circuit in Fig. 3, we will obtain the α and ε as
α=+( )
++( )
g g
g g g
g g
g g gm m
m m m
m m
m m m
4 13
12 2 4
2 9
8 2 4
, (7)
and
ε=
− +
+( )−
I g g
g g
I g g
g g
I
g g
g
g
g
B m m
m m
B m m
m m
B
m m
m
m
m
1 4 13
3 12
1 2 9
1 8
1
2 4
2
1
4
gg
g g
g
g g
gm
m m
m
m m
m3
4 13
12
2 9
8
+
. (8)
inV3M
1M 2M
4M
4I
2I
1BI
1BI
inI
DDV
SSV
FIGURE 2Class AB translinear loop.
FIGURE 3A CMOS-based second generation current controlled current conveyor.
realization of cMoS ccccta and itS applicationS 39
If g g g g g g g gm m m m m m m m1 4 2 4 8 9 12 13= = = =, , and , then the output current can be found to be
I Iz x= . (9)
The output resistance looking into the z terminal (rz) can be respectively
expressed as
rr r
r rzo o
o o
≅+9 13
9 13
, (10)
where ro is the drain-source resistance seen at the mentioned output terminal.
2.3 Transconductance AmplifierIn this section, a simple differential pair amplifier [6] is employed to achieve simpler circuit description of the proposed CCCCTA as shown in Fig. 4. From Fig. 4, transistors M
14 and M
15 function as a differential amplifier to
convert an input voltage to an output current. M16
and M17
work as a simple current mirror when I
B2 is an input bias current. When V
in is applied, this
makes ID14
and ID15
flowing in M14
and M15
, respectively. The relationship of Io
and Vin of the transconductance amplifier is given by
I g V g VO m m= − +β β1 14 1 2 15 2 , (11)
where β1 and β
2 are transconductance ratios. By straightforward analysis of
circuit in Fig. 4, we will obtain the β1 and β
2 as
β117
16
15 16 14 17
16 14 15
= +−( )+( )
g
g
g g g g
g g gm
m
m m m m
m m m
, (12)
FIGURE 4The simple transconductance amplifier.
40 M. Siripruchyanun et al.
β215 16 14 17
16 14 15
1= −−( )+( )
g g g g
g g gm m m m
m m m
, (13)
and
=−−( )+( )
I g g g g
g g gB m m m m
m m m
15 16 14 17
16 14 15
. (14)
If g g g g gm m m m m14 15 16 17= = = and , Eq. (11) can be expressed as
I g V VO m= −( )1 2 , (15)
where g Im n B= β 2 .
The output resistance looking into the x terminal (ro) can be respectively
expressed as
rr r
r rOo o
o o
≅+
15 17
15 17
. (16)
2.4 Proposed Current Controlled Current Conveyor Transconductance Amplifier
The proposed CCCCTA consists of two principal blocks: a current controlled second generation current conveyor (CCCII) circuit and an operational transconductance amplifier (OTA) circuit. The proposed realization of the CCCCTA in a CMOS technology to achieve a wide-range of frequency responses is shown in Fig. 5. The circuit implementation consists of mixed translinear loop (M
1-M
4). The mixed loop is DC biased by using current mir-
rors (M5-M
7 and M
10-M
11). The R
x can be obtained by Eq. (2). The output
z-terminal that generates the current from x terminal is realized using transis-tors (M
8-M
9 and M
12-M
13). The simple-version transconductance amplifier is
FIGURE 5Completely proposed current controlled current conveyor transconductance amplifier.
realization of cMoS ccccta and itS applicationS 41
realized using transistors (M14
-M17
), whose transconductance gain can be adjusted by I
B2.
3 SIMulATIOn ReSulTS
To prove the performances of the proposed CCCCTA, the PSPICE simulation program was used. The PMOS and NMOS transistors employed in the pro-posed element in Fig. 2 were simulated by respectively using the parameters of a 0.35 µm TSMC CMOS technology [7] with ±1.5 V supply voltages. The aspect transistor ratios of PMOS and NMOS are listed in Table 1. Fig. 6 depicts the parasitic resistance R
x at input terminal when I
B1 has varied. Fig. 7
shows the transconductance value when IB2
was varied from 1 200µ µA A− .Fig. 8 displays DC transfer characteristic of the proposed CCCCTA,
when I A AB1 10 50= µ µ, and 100µA. So it is seen that it is linear in range of − ≤ ≤7 7mA I mAx . Moreover, the bandwidths of output terminals are shown in Fig. 9. We found that the –3dB bandwidth of I I V V I Iz x x y o x/ , / , / and I Vo y/ are respectively located at 333.48 MHz, 4.12 GHz, 107.34 MHz and 115.22 MHz. The summarized properties of the CMOS CCCCTA are shown in Table 2.
TABlE 1Dimensions of the MOS transistors.
CMOS Transistors W(µm) / L(µm)
M1-M2
M3-M4
M5, M7
M6
M8-M9
M10-M11
M12-13
M14-M17
12/1
4/1
10/1
8/1
10/5
30/1
30/5
30/5
RX(Ω
)
IB1(A)1.0n 10n 100n 1.0µ 10µ 100µ 300µ
1.0k
1.0M
10
10M
fIguRe 6Parasitic resistance at x terminal relative to I
B1.
42 M. Siripruchyanun et al.
0 40 80 120 160 2000.2
0.4
0.5
0.8
1
Tra
nsco
nduc
tanc
e (m
S)
IB2(µA)20 60 100 140 180
FIGURE 7Transconductance value relative to I
B2.
FIGURE 8DC transfer characteristic of the CCCCTA.
Ix (mA)-1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0-1.0
0
1.0IB1=10µAIB 1=50µAIB 1=100µA
I z(m
A)
FIGURE 9Frequency responses at output terminals.
Frequency(Hz)1.0k 10k 100k 1.0M 10M 100M 1.0G 10G
-40
-20
0
10
Gai
n(dB
)
IZ/IXVX/VY
IB1=50µA
(a)
Frequency(Hz)1.0k 10k 100k 1.0M 10M 100M 1.0G 10G
-80
-40
0
40
Gai
n (d
B)
IO/IXIO/VY
IB1=50µAIB2=100µA
(b)
realization of cMoS ccccta and itS applicationS 43
4 APPlICATIOn exAMPleS
4.1 digitally-programmable current-mode universal biquad filterThe first application of the proposed CCCCTA is a current-mode biquad filter shown in Fig. 10. It employs only one active element and 2 grounded capaci-tors, which is easy to fabricate, differing from previous circuits [8–9]. The CCCCTA in Fig. 10 is slightly modified from the proposed CCCCTA in Fig. 5 by using dual-output CCCCTA which can be easily achieved by using the current mirrors to copy current from z
1 to z
2 terminal to extend the usabil-
ity of the CCCCTA. Straightforwardly analyzing the circuit in Fig. 10 and using CCCCTA properties in section 2, the transfer functions of the network can be obtained as 2nd
II sC g I I s C C R sC g
s C C R sC gO
in m in in x m
x m
=+ − + +( )
+ +1 2 2 3
21 2 2
21 2 2
. (17)
From Eq. (17), the magnitudes of current inputs Iin1
, Iin2
and Iin3
are chosen as in Table 3 to obtain a standard function of the 2nd order network. The circuit for selection can be seen in [10]. From Eq. (17), the pole frequency (ω
0) and
quality factor (Q0) of each filter response can be expressed as
TABlE 2Conclusions of the CMOS CCCCTA parameters.
Parameters Values
Power supply voltages ±1.5 V
Power consumption 899 µW
3dB Bandwidth 333.48 MHz(Iz/Ix),
4.12 GHz(Vx/Vy),
107.34 MHz(Io/Ix),
115.22 MHz(Io/Vy)
Input current linear range –0.7 mA to 0.7 mA
Rx range 491.09 Ω-15.76 MΩ
Input bias current range for controlling Rx
1nA-95.29 µA
Transconductance range 0.28 mS–1 mS
Input bias range for controlling transconductance amplifier 1 µA–180 µA
Rz
140.16 kΩ
Ro
207.87 kΩ
Ry
9.32 MΩ
44 M. Siripruchyanun et al.
ω01 2
=g
C C Rm
x
, (18)
and
QC R g
Cx m
01
2
= . (19)
Substituting the intrinsic resistance and transconductance as depicted in Eqs. (2) and (3) into Eqs. (18) and (19), it yields
ω β01 2
1 2
1 2
8=
nB BI I
C C
/
, (20)
FIGURE 10Current-mode universal biquad filter based on the CCCCTA.
1BI
x
y 1z
oCCCCTA
2BI
2z
2C
1C1inI
2inI 3inIOI
TABlE 3The I
in1, I
in2 and I
in3 value selections for each filter function response.
filter Responses Input
Io
Iin1
Iin2
Iin3
BP 1 0 0
HP 1 1 1
lP 0 1 0
BR 1 0 1
AP 2 0 1
realization of cMoS ccccta and itS applicationS 45
and
QC I
C I
B
B
01 2
2 1
1 2
=
/
. (21)
From Eqs. (20) and (21), by maintaining the ratio of IB1
and IB2
constant, the pole frequency can be adjusted by I
B1 and I
B2 without affecting the quality
factor.To prove the performances of the proposed circuit, the PSPICE simulation
program was used. C1= C
2= 1nF, I
B1 = 50 µA, I
B2= 150 µA are chosen to
obtain resistance and transconductance values of 2.59 kΩ and 0.236 mS, respectively. This yields the pole frequency of 53.70 kHz. Calculated value of this parameter from Eq. (18) is 48.06 kHz. The results shown in Fig. 11 are the gain and phase responses of the proposed biquad filter obtained from Fig. 11. There are clearly seen that the proposed biquad circuit can provide low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on selections as shown in Table 3, without modifying circuit topology.
Fig. 12 displays magnitude responses of band-pass function for different I
B values. It is shown that the pole frequency of the responses can be adjusted
by the input bias current IB1
.
4.2 grounded Inductance SimulatorThe grounded inductance simulator based on the CCCCTA is shown in Fig. 13. It employs only single CCCCTA, which contrasts to ordinarily proposed circuits [11–12]. From routine analysis and using the CCCCTA properties, an input impedance of the circuit can be written as
ZV
I
sCR
ginin
in
x
m
= = . (22)
From Eq. (22), it is obvious that the circuit shown in Fig. 13 performs a grounded inductance with a value
ZV
I
sCR
ginin
in
x
m
= = . (23)
From Eq. (23), the inductance value Leq
can be adjusted electronically by either I
B1 or I
B2.
The impedance and phase of the simulator relative to frequency, which are compared to ideal inductor are also shown in Fig. 14 where C = 1nF, I
B1 = 30 µA and I
B2 = 100 µA. Fig. 15 shows impedance values relative to fre-
quency of the simulator for different IB2
.
46 M. Siripruchyanun et al.
FIGURE 11Gain and phase responses of the biquad filter in Fig. 10 (a) lP (b) HP (c) BP (d) BR (e) AP.
Frequency (Hz)1.0k 3.0 10k 30k 100k 300k 1.0M 3.0M-200d
-100d
0
-80
-40
0
40
Phas
e
Gai
n (d
B)
GainPhase
(a)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-200d
-100d
0
-80
-40
0
40
Phas
e
Gain
(dB) Gain
Phase
(b)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-100d
0
100d
-40
-20
0
Gain
(dB)
Pha
se
GainPhase
(c)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-100d
0
100d
-40
-20
0
20
GainPhase
Phas
e
Gai
n (d
B)
(d)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M
-100d
0
100d
-180d
180d
-5
0
5
Phas
e
Gai
n (d
B)
GainPhase
(e)
realization of cMoS ccccta and itS applicationS 47
FIGURE 12Band-pass responses for different values of I
B.
Frequency (Hz)3.0k 10k 30k 100k 300k 1.0M 3.0M-50
-25
010
Gai
n (d
B)
IB 1=IB2=5μAIB1=IB2=20μAIB 1=IB 2=120μA
C1=1nF, C2=0.1nF
FIGURE 14The impedance and phase relative to frequency of the grounded inductance simulator.
Frequency(Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M 10M
10k
10
10M
-100d
-50d
0d
50d
100d
Pha
se
Impe
dan
ce (
Ω)
IdealSimulated
ImpedancePhase
IB1=30µAIB2=100µA
FIGURE 13Grounded inductance simulator based on the CCCCTA.
FIGURE 15The impedance values relative to frequency of the simulators with different I
B2.
Frequency (Hz)1.0k 10k 100k 1.0M 10M 100M
100
10k
1.0M
10
10M
IB2=100µA
IB2=200µA
IB2=300µA
Impe
dan
ce (Ω
)
48 M. Siripruchyanun et al.
4.3 Sinusoidal OscillatorThe sinusoidal oscillator based on the CCCCTA is shown in Fig. 16. It con-sists of single output CCCCTA and 2 grounded capacitors. Considering the circuit in Fig. 16 and using the CCCCTA properties, it yields characteristic equation of this circuit as
s C C R s C C gx m2
1 2 1 2 0+ −( )+ = . (24)
From Eq. (24), it can obviously seen that the proposed circuit can be set to be a sinusoidal oscillator if
C C1 2= . (25)
Eq. (25) is called as the condition of oscillation. Then the characteristic equa-tion of the system becomes
sg
C C Rm
x
2
1 2
0+ = . (26)
From Eq. (26), the oscillation frequency of this system can be obtained as
ω β01 2
1 2
1 2
1 2
8= =
g
C C R
I I
C Cm
xn
B B
/
. (27)
It can be seen that, from Eq. (27), the oscillation frequency (ω0) can be con-
trolled by bias current. The confirmed result of the oscillator can be seen in Fig. 17. They show the responses of oscillator with bias currents: I
B1 and I
B2
are respectively set to 50 µA and 100 µA. Fig. 18 shows the simulated output spectrum, where the total harmonic distortion (THD) is about 1.07%.
FIGURE 16Oscillator based on the CCCCTA.
realization of cMoS ccccta and itS applicationS 49
4.4 Voltage-mode universal Biquad filterThe final application of the proposed CCCCTA depicted in this paper is a voltage-mode universal biquad filter shown in Fig. 19. For straightforward analysis of the circuit in Fig. 19 and using CCCCTA properties in section 2, the transfer functions of the network can be obtained as
VV s C C V sC G V G g
s C C sC G G gOin in in x m
x m
=+ ++ +
12
1 2 2 2 1 32
1 2 2 1
. (28)
FIGURE 17The output waveform obtained from the oscillator in Fig. 16.
Time (µs)0 10 20 30 40 50 60 70 80 90 100-200
0
200
VO
(mV
)
C1=0.1nFC2=0.11nF
FIGURE 18The simulation result of output spectrum.
Frequency (Hz)0 100k 200k 300k 400k 500k 600k 700k 800k 900k 1M0
100
200
VO
(mV
) C1=0.1nFC2=0.11nFTHD=1.07%
FIGURE 19Voltage-mode universal biquad filter based on the CCCCTA.
50 M. Siripruchyanun et al.
From Eq. (28), the magnitudes of input voltages: Vin1,
Vin2
and Vin3
are chosen as in Table 4 to obtain a standard function of the 2nd order network. From Eq. (28), the pole frequency (ω
0) and quality factor (Q
0) of each filter response
can be expressed as
ω β01 2
1 2
1 2
1 2
8= =
g
C C R
I I
C Cm
xn
B B
/
. (29)
and
Q RC R g
C
C I
C Ix m B
B
0 11
2
1 2
2 1
1 2
= =
/
. (30)
It is either found that, from Eqs. (29) and (30), the quality factor can be adjusted by R
1 without affecting the pole frequency. Reversely, the pole fre-
quency can be controlled via Rx or g
m.
To prove the performances of the proposed circuit, the PSPICE simulation program was also used. C C nF1 2 1= = , I A I AB B1 250 150= =µ µ, and R k1 4 7= Ω. are chosen. The results shown in Fig. 20 are the gain and phase responses of the proposed biquad filter obtained from Fig. 19. It is seen that the proposed biquad circuit can provide low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on selection as shown in Table 4, without modifying circuit topology. Fig. 21 displays gain responses of band-pass function for different R
1 values. It is shown that the quality factor
can be controlled by R1 without affecting the pole frequency.
TABlE 4The V
in1, V
in2 and V
in3 value selections for each filter function response.
filter Responses Input
V0
Vin1
Vin2
Vin3
BP 0 1 0
HP 1 0 0
lP 0 0 1
BR 1 0 1
AP 1 -1 1
realization of cMoS ccccta and itS applicationS 51
FIGURE 20Gain and phase responses of the biquad filter in Fig. 19 (a) lP (b) HP (c) BP (d) BR (e) AP.
Frequency (Hz)1.0k 3.0 10k 30k 100k 300k 1.0M 3.0M-200d
-100d
0
-80
-40
0
40
Ph
ase
Gai
n (d
B)
GainPhase
(a)
Frequency (Hz)
1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M0d
90d
180d
-80
-40
0
40
Ph
ase
Gai
n (d
B)
GainPhase
(b)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-100d
0
100d
-40
-20
0
Gai
n (d
B)
Ph
ase
GainPhase
(c)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-100d
0
100d
-40
-20
0
20
GainPhase
Pha
se
Ga
in (
dB)
(d)
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M
-100d
0
100d
-180d
180d
-5
0
5
Pha
se
Ga
in (
dB)
GainPhase
(e)
52 M. Siripruchyanun et al.
FIGURE 21Band-pass responses for different values of R
1.
Frequency (Hz)1.0k 3.0k 10k 30k 100k 300k 1.0M 3.0M-50
-25
0
R1=2kΩR1=4.7kΩR1=10kΩ
Gain
(dB)
5 COnCluSIOn
The new basic building block, called CCCCTA, has been introduced via this paper. The usabilities have been proven by the simulation and application examples. They consume few numbers of components while electronic control-lability is still available, which differs from the recently proposed elements. This modified element is very appropriate to realize in commercially-purposed integrated circuit. Our future work is to find more applications of the CCCCTA, emphasizing on analog signal processing circuits such as multiplier/divider, rectifier, etc.
RefeRenCeS
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