An Electronically Controllable Dual-Mode Universal ... - IEEE Xplore
An Electronically Controllable Dual-Mode Universal Biquad Filter Using Only Single CCCCTA Winai Jaikla
Pisede Sornklin
Electric and Electronic Program, Faculty of Industrial Technology, Suan Sunandha Rajabhat University Dusit, Bangkok, 10300, Thailand Tel: +66-2-243-2240 Ext. 317 Email: [email protected]
Department of Electronic, Faculty of Electrical and Electronic, Surin Technical College, Muang, Surin, 3200, Thailand Tel: +66-44-511-190 Email: [email protected]
Abstract— This article presents a dual-mode (voltage-mode and current-mode) universal biquadratic filter performing completely standard functions: low-pass, high-pass, band-pass, band-reject and all-pass functions, based on plus type dualoutput current controlled current conveyor transconductance amplifier (CCCCTA). The features of the circuit are that: the quality factor and natural frequency can be tuned electronically via the input bias currents: the circuit description is very simple, consisting of merely single CCCCTA and 2 capacitors: the circuit can provide either the voltage-mode or current-mode filter without changing circuit topology. Additionally, each function response can be selected by suitably selecting input signals with digital method. Without any external resistors, the proposed circuit is very suitable to further develop into an integrated circuit. The PSPICE simulation results are depicted. The given results agree well with the theoretical anticipation. The maximum power consumption is approximately 1.81mW at ±1.5V supply voltages.
I.
INTRODUCTION
An analog filter is an important block and widely used for continuous-time signal processing. It can be found in many fields: for instance, communication, measurement and instrumentation and control systems [1-2]. One of most popular analog filters is a universal biquadratic filter since it can provide several functions. Nowadays, a universal filter working in current-mode has being been more popular than voltage-mode one. Since the last decade, there has been much effort to reduce the supply voltage of analog systems. This is due to the command for portable and battery-powered equipment. Since a low-voltage operating circuit becomes necessary, the current–mode technique is ideally suited for this purpose. Actually, a circuit using the current-mode technique has many other advantages: for example, larger dynamic range, higher bandwidth, greater linearity, simpler circuitry and lower power consumption [3-4]. However, in present, the voltage-mode circuits are still used in some applications.
Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800, Thailand Tel: +66-2- 913-2500 Ext. 3328 Email: [email protected] of analog signal processing [5]. The fact that the device can operate in both current and voltage-modes provides flexibility and enables a variety of circuit designs. In addition, it can offer advantageous features such as high-slew rate, higher speed, wide bandwidth and simple implementation [5]. However, the CCTA can not control the parasitic resistance at X (Rx) 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, high power consumption and without electronic controllability. On the other hand, the introduced current-controlled current conveyor transconductance amplifier (CCCCTA) [6-7] has the advantage of electronic adjustability over the CCTA. In many applications, voltage and current-mode circuits are used to be connected which causes some difficulties that can be overcame by using voltage-to-current and current-tovoltage converters at the interface of these circuits. During V-I interfacing, it is also possible to perform signal processing at the same time so that the total effectiveness of the electronic circuitry can be increased [8]. The literature surveys show that the dual-mode universal filter circuits using different highperformance active building blocks such as OTAs [9-11], current feedback op-amps (CFOAs) [12-14], Four-Terminal Floating Nullors (FTFNs) [15-17] and current conveyors [1822], have been reported. Unfortunately, these reported circuits suffer from one or more of following weaknesses:
The current conveyor transconductance amplifier (CCTA) is a reported active component, especially suitable for a class
978-1-4244-2342-2/08/$25.00 ©2008 IEEE.
Montree Siripruchyanun
1144
a)
Excessive use of the active and/or passive elements [8, 12-15, 17-22]. b) Require changing circuit topologies to achieve several functions [9-10, 13-15]. c) Lack of electronic adjustability [8, 12-15, 17-21]. d) Can not provide completely standard functions [8-9, 11, 13-14, 17-18, 20]. e) Can not provide functions both in voltage and current-modes with the same topology [11, 13, 15, 17].
This work is arranged to propose a new voltage/current– mode universal biquadratic filter, emphasizing on use of single CCCCTA. The features of proposed circuit are that: the proposed universal filter can provide completely standard functions both in voltage-mode and current-mode without changing circuit topology by appropriately selecting the input signals: the circuit description is very simple, it consists of 1 CCCCTA and 2 capacitors, which is suitable for fabricating in monolithic chip: the filter does not require any external resistor. In addition, the natural frequency and the bandwidth can be tuned electronically by adjusting the bias currents. Its performances are illustrated by PSPICE simulations, they show good agreement as mentioned. II.
⎛ 1 gm gm ⎞ + Vin 2 ⎜ s + ⎟ C1 C R C C 1 2 Rx ⎠ . ⎝ 1 x gm 1 s2 + s + C1 Rx C1C2 Rx
Vin1 s 2 + Vin 3 s VO =
I B1 I in1
Vin1
Basic Concept of CCCCTA The CCCCTA properties are similar to the conventional CCTA, except that the CCCCTA has finite input resistance Rx at the x input terminal. This parasitic resistance can be controlled by the bias current IB1 as shown in the following equation
o
y
CCCCTA z2 z1
Vin 2
CIRCUIT PRINCIPLE
I in 2
0 0 0 ⎤ ⎡Ix ⎤ ⎢ ⎥ 1 0 0 ⎥⎥ ⎢Vy ⎥ , 0 0 0 ⎥ ⎢Vz1 ⎥ ⎥⎢ ⎥ 0 ± g m 0 ⎦ ⎣⎢Vo ⎦⎥
Rx =
TABLE I.
THE
Vin1 , Vin 2
Vy
Vx
iy
ix
y x
CCCCTA z1
o
x
z2 iz 1
Vz 1
y
iz 2
Vz 2
Vin 3
Filter Responses BP
(2)
gmVz 1 io
AND
VALUE SELECTIONS FOR EACH
FILTER FUNCTION RESPONSE
VT I , gm = B 2 . 2 I B1 2VT
IB2
I in 3
C2
From Eq. (3), Vin1, Vin2 and Vin3 can be chosen as in Table I to obtain a standard function of the 2nd–order network. From Table I, it should be remarked that, in case of the BP, BR, AP and LP, the circuit condition: Rx=1/gm is required.
(1)
g m is the transconductance of the CCCCTA and VT is the thermal voltage. The symbol and the equivalent circuit of the CCCCTA are illustrated in Fig. 1(a) and (b), respectively.
I B1
IO
Figure 2. Proposed dual-mode universal filter
VO
where
Vo
Vin 3
A.
⎡ I y ⎤ ⎡0 ⎢ ⎥ ⎢ ⎢Vx ⎥ = ⎢ Rx ⎢I ⎥ ⎢1 ⎢ z1, z 2 ⎥ ⎢ ⎢⎣ I o ⎥⎦ ⎣ 0
IB2
x
C1
(3)
1 ix Rx
(Rx=1/gm)
HP
Input selections Vin1
Vin2
Vin3
0
0
1
1
0
0
BR
(Rx=1/gm)
1
1
-1
AP
(Rx=1/gm)
1
1
-2
LP
(Rx=1/gm)
0
1
-1
For current-mode case, where Vin1=Vin2=Vin3=0, straightforwardly analyzing the circuit in Fig. 2, the output current can be obtained as
o
I in1 s IO =
⎛ gm gm 1 1 + I in 2 − I in3 ⎜ s 2 + s + C1 Rx C1C2 Rx C1 Rx C1C2 Rx ⎝ gm 1 s2 + s + C1 Rx C1C2 Rx
⎞ ⎟ ⎠.
(4)
From Eq. (4), the magnitudes of input currents Iin1, Iin2 and Iin3 can be chosen as in Table II to obtain a standard function of the network. The circuit of digital selection can be seen in [23]. From Eqs. (3)-(4), for dual-mode, the natural frequency (ω0) and quality factor (Q0) of each filter response can be expressed as
z1 z2 iz 1 = iz 2 = ix
Figure 1. CCCCTA (a) Symbol (b) Equivalent circuit
B. Proposed Dual-Mode Universal Biquad Filter The proposed dual-mode universal filter is shown in Fig. 2, where IB1 and IB2 are input bias currents of CCCCTA. They are used to control the corresponding parasitic resistance and transconductance gain. For voltage-mode case, where Iin1=Iin2=Iin3=0, straightforwardly analyzing the filter in Fig. 2, the output voltage can be obtained as
ω0 =
gm C1 g m , Q0 = . C1C2 Rx C2 Rx
(5)
Substituting intrinsic resistance and transconductance as depicted in Eq. (2), it yields
1145
ω0 =
1 VT
I B1 I B 2 C1 I B 2 , Q0 = . C1C2 C2 I B1
(6)
From Eq. (6), by maintaining the ratio IB1 and IB2 to be constant, it can be remarked that the natural frequency can be adjusted by IB1 and IB2 without affecting the quality factor. In addition, bandwidth (BW) of the system can be expressed by BW =
ω0
=
Q0
2 I B1 . C1VT
(7)
We found that the bandwidth can be linearly controlled by IB1. Moreover, it can be seen that the natural frequency can be also adjusted orthogonally from the bandwidth by varying IB2. TABLE II.
THE
I in1 , I in 2
AND
I in3
Iin1 1 1 1 2 0
Q
Input selections Iin2 0 1 0 0 1
Iin3 0 1 1 1 0
I B1 Q1
(10)
= −1
Therefore, all the active and passive sensitivities are equal or less than unity in magnitude. D. Non-ideal case For non-ideal case, the I z and I o of CCCCTA can be respectively characterized by Vx = β Vy + I x Rx , I z1 = α1 I x , I z 2 = α 2 I x , I o = γ g mVz1 , (11)
α , γ and β are transferred error values deviated from one. In the case of non-idea and reanalysis of proposed filter circuit in Fig. 2, it respectively yields output voltage and current as ⎛ β α βγ g m + Vin 2 ⎜ s + 1 C1 ⎝ C1 Rx C1C2 Rx αγg 1 + 1 m s2 + s C1 Rx C1C2 Rx
Vin1 s 2 + Vin 3 s VO =
I in1 s IO =
α2 C1 Rx
+ I in 2
γ gm
⎞ ⎟ ⎠,
⎛ g mα1α 2γ αα γg 1 − I in 3 ⎜ s 2 + s + 1 2 m C1C2 Rx C1 Rx C1C2 Rx ⎝ α1γ g m 1 2 + s +s C1 Rx C1C2 Rx
In this case, the ω0 and Q0 are changed to
Q8
Q9
Q6
Q7
Q14 Q15
z1
Q4
Q3
Q14
Q5
VCC
Q16
o
z2
x
III.
(8)
= 1; S
=S
Q2
Q13
Q15
Q23
IB2
VEE
Figure 3. Internal construction of CCCCTA
(9)
S
11
y
1 1 S IQB02 = SCQ10 = ; S IQB01 = SCQ20 = − 2 2, BW C1
Q12
Q
10
1 1 S IωB01 , I B 2 = , SCω10,C2 = − , SVωT0 = −1, 2 2
BW VT
α1γ C1 Rx g m
VALUE SELECTIONS FOR EACH
C. Circuit Sensitivities The sensitivities of the proposed circuit can be found as
BW I B1
, Q0 =
, (14) C1C2 Rx C2 while BW is still equal to Eq. (7). Actually, these deviations are very small and can be ignored. Practically, from Eqs. (1114), α, γ and β originate from intrinsic resistances and stray capacitances in the active elements. These errors affect the sensitivity to temperature and high frequency response of the proposed circuit. From Eq. (14), it is found that the pole frequency and quality factor depend on the temperature and frequency variations, then the CCCCTA should be carefully designed to achieve these errors as low as possible.
FILTER FUNCTION RESPONSE
Filter Responses IO BP HP BR AP LP
α1γ g m
ω0 =
(12)
SIMULATION RESULTS
To prove the performances of the proposed circuit, the PSPICE simulation program was used. The PNP and NPN transistors employed in the proposed circuit were simulated by respectively using the parameters of the PR200N and NR200N bipolar transistors of ALA400 transistor array from AT&T [24]. Fig. 3 depicts schematic description of the CCCCTA used in the simulations. The circuit was biased with ±1.5V supply voltages. C1=C2=1nF and IB1=54µA, IB2=200µA are chosen. It yields the natural frequency of 540.75kHz, while calculated value of this parameter from Eq. (7) is 612.45kHz. The results shown in Fig. 4 are the gain and phase responses of the proposed biquad filter in voltage-mode obtained from Fig. 2. There are seen that the proposed filter in voltage-mode can provide low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on selection as shown in Table I, without modifying circuit topology. The gain and phase responses of the proposed biquad filter in current-mode are also investigated, which are similar to those of voltage-mode. Fig. 5 shows gain responses of current-mode band-pass function where IB1 and IB2 are equally set to keep the ratio to be constant and changed for several values. It is found that pole frequency can be adjusted without affecting the quality factor, as depicted in Eq. (6). Maximum power consumption is about 1.81mW. IV.
⎞ ⎟ ⎠ . (13)
CONCLUSIONS
The dual-mode universal biquadratic filter based on single CCCCTA has been presented. The advantages of the proposed circuit are that: it performs low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on an appropriate selection of three signals in dual-mode: the quality factor and the pole frequency can be electronically controlled via input bias currents, it is easily modified to use in control systems using a microcontroller [3]. The circuit description comprises
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REFERENCES [1] [2]
[3] [4]
[5]
[6]
[7]
[8] [9] [10] [11]
[12]
[13]
[14]
[15] [16] [17]
[18]
[19]
[20]
[21]
A. S. Sedra, and K. C. Smith, Microelectronic circuits, 5th ed., Florida: Holt, Rinehart and Winston, 2003. M. A. Ibrahim, S. Minaei, and H. A. Kuntman, “A 22.5 MHz currentmode KHN-biquad using differential voltage current conveyor and grounded passive elements,” Int. J. Electron. Commun. (AEU), vol. 59, pp. 311-318, 2005. C. Toumazou, F. J. Lidgey, and D. G. Haigh, Analogue IC design: the current-mode approach, London: Peter Peregrinus, 1990. D. R. Bhaskar, V. K. Sharma, M, Monis, and S. M. I. Rizvi, “New current-mode universal biquad filter,” Microelec. Journal, vol. 30, pp. 837-839, 1999. R. Prokop, V. Musil, “New modern circuit block CCTA and some its applications,” Proceeding of ET'2005, Book 5. Sofia: TU Sofia, pp. 9398, 2005. M. Siripruchyanun and W. Jaikla, “Current controlled current conveyor transconductance amplifier (CCCCTA): a building block for analog signal processing,” Proceeding of ISCIT 2007, Sydney, Australia, pp. 1072-1075, 2007. M. Siripruchyanun, M. Phattanasak and W. Jaikla, “Current Controlled Current Conveyor Transconductance Amplifier (CCCCTA): A Building Block for Analog Signal Processing,” 30th Electrical Engineering Conference (EECON-30), pp. 897-900, 2007. N. A. Shah and M. A. Malik, “Multifunction mixed-mode filter using FTFNs,” Analog ICs and Signal Processing, vol. 47, pp. 339-343, 2006. J. WU and E. I. EL-Masry, “Universal voltage- and current-mode OTAs based biquads,” Int. J. Electronics, vol.85, pp. 553-560, 1998. D. R. Bhaskar, R. K. Sharma, A. K. Singh, R. Senani, “New Dualmode Biquads Using OTAs,” Frequenz, vol. 60, pp. 246-252, 2006. D. R. Bhaskar, A. K. Singh, R. K. Sharma and R. Senani, “New OTAC universal current-mode/trans-admittance biquads,” IEICE Electron. Express, vol. 2, pp.8-13, 2005. N. Pandey, S. K. Paul, A. Bhattacharyya and S. B. Jain, “A new mixed mode biquad using reduced number of active and passive elements,” IEICE Electron. Express, vol. 3, pp.115-121, 2006. C. L. Hou, C. C. Huang, Y. S. Lan, J. J. Shaw and C. M. Chang, “Current and voltage-mode universal biquads using a single currentfeedback amplifier,” Int. J. Electronics, vol. 86, pp. 929-932, 1999. N. A. Shah and M. A. Malik, “Voltage/current-mode universal filter using FTFN and CFA,” Analog ICs and Signal Processing, vol. 45, pp. 197-203, 2005. S. T. Liu and J. L. Lee, “Insensitive current/voltage-mode filters using FTFNs,” Electronics Letters, vol. 32, pp.1079 –1080, 1996. N. A. Shah and M. A. Malik, “Multifunction mixed-mode filter using FTFNs,” Analog ICs and Signal Processing, vol. 47, pp. 339-343, 2006. N. A. Shah S. Z. Iqbal and B. Parveen, “SITO high output impedance transadmittance filter using FTFNs,” Analog ICs and Signal Processing, vol. 40, pp. 87-89, 2004. C. L. Hou and C. C. Lin, “A filter with three voltage-inputs and one voltage-output and one current-output using current Conveyors,” Tamkang Journal of Sci. and Eng., vol. 7, pp. 145-148, 2004. N. Pandey, S. K. Paul, A. Bhattacharyya and S. B. Jain, “A new mixed mode biquad using reduced number of active and passive elements,” IEICE Electron. Express, vol. 3, pp.115-121, 2006. A. Toker, O. ÇiÇekoglu, S. Özcan and H. Kuntman, “High output impedance transadmittance type continuous time multifunction fillter with minimum active elements,” Int. J. Electronics, vol.88, pp. 10851091, 2001. M. T. Abuelma'atti and A. Bentrcia, “A novel mixed-mode CCII-based filter,” Active and Passive Electronic Components, vol. 27, pp. 197205, 2004.
[22] M. T. Abuelma'atti, “A novel mixed-mode current-controlled currentconveyor-based filter,” Active and Passive Electronic Components, vol. 26, pp. 185-191, 2003. [23] W. Tangsrirat, “Low-voltage digitally programmable current-mode universal biquadratic filter,” Int. J. Electron Commun (AEU), Available online 26 April 2007. [24] D. R. Frey, “Log-domain filtering: an approach to current-mode filtering,” IEE Proc. Circuit Devices, vol. 140, pp. 406-416, 1993.
(a)
(b)
(c)
(d)
(e)
Figure 4. Gain and phase responses of the biquad filter in voltage-mode for (a) LP (b) HP (c) BP (d) BR (e) AP
Gain (dB)
only 1 CCCCTA and 2 capacitors. With mentioned features, it is very suitable to realize the proposed circuit in monolithic chip to use in battery-powered, portable electronic equipments such as wireless communication system devices.
Figure 5. Current-mode band-pass responses for different values of IB1 and IB2
1147
Pisede Sornklin
Electric and Electronic Program, Faculty of Industrial Technology, Suan Sunandha Rajabhat University Dusit, Bangkok, 10300, Thailand Tel: +66-2-243-2240 Ext. 317 Email: [email protected]
Department of Electronic, Faculty of Electrical and Electronic, Surin Technical College, Muang, Surin, 3200, Thailand Tel: +66-44-511-190 Email: [email protected]
Abstract— This article presents a dual-mode (voltage-mode and current-mode) universal biquadratic filter performing completely standard functions: low-pass, high-pass, band-pass, band-reject and all-pass functions, based on plus type dualoutput current controlled current conveyor transconductance amplifier (CCCCTA). The features of the circuit are that: the quality factor and natural frequency can be tuned electronically via the input bias currents: the circuit description is very simple, consisting of merely single CCCCTA and 2 capacitors: the circuit can provide either the voltage-mode or current-mode filter without changing circuit topology. Additionally, each function response can be selected by suitably selecting input signals with digital method. Without any external resistors, the proposed circuit is very suitable to further develop into an integrated circuit. The PSPICE simulation results are depicted. The given results agree well with the theoretical anticipation. The maximum power consumption is approximately 1.81mW at ±1.5V supply voltages.
I.
INTRODUCTION
An analog filter is an important block and widely used for continuous-time signal processing. It can be found in many fields: for instance, communication, measurement and instrumentation and control systems [1-2]. One of most popular analog filters is a universal biquadratic filter since it can provide several functions. Nowadays, a universal filter working in current-mode has being been more popular than voltage-mode one. Since the last decade, there has been much effort to reduce the supply voltage of analog systems. This is due to the command for portable and battery-powered equipment. Since a low-voltage operating circuit becomes necessary, the current–mode technique is ideally suited for this purpose. Actually, a circuit using the current-mode technique has many other advantages: for example, larger dynamic range, higher bandwidth, greater linearity, simpler circuitry and lower power consumption [3-4]. However, in present, the voltage-mode circuits are still used in some applications.
Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800, Thailand Tel: +66-2- 913-2500 Ext. 3328 Email: [email protected] of analog signal processing [5]. The fact that the device can operate in both current and voltage-modes provides flexibility and enables a variety of circuit designs. In addition, it can offer advantageous features such as high-slew rate, higher speed, wide bandwidth and simple implementation [5]. However, the CCTA can not control the parasitic resistance at X (Rx) 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, high power consumption and without electronic controllability. On the other hand, the introduced current-controlled current conveyor transconductance amplifier (CCCCTA) [6-7] has the advantage of electronic adjustability over the CCTA. In many applications, voltage and current-mode circuits are used to be connected which causes some difficulties that can be overcame by using voltage-to-current and current-tovoltage converters at the interface of these circuits. During V-I interfacing, it is also possible to perform signal processing at the same time so that the total effectiveness of the electronic circuitry can be increased [8]. The literature surveys show that the dual-mode universal filter circuits using different highperformance active building blocks such as OTAs [9-11], current feedback op-amps (CFOAs) [12-14], Four-Terminal Floating Nullors (FTFNs) [15-17] and current conveyors [1822], have been reported. Unfortunately, these reported circuits suffer from one or more of following weaknesses:
The current conveyor transconductance amplifier (CCTA) is a reported active component, especially suitable for a class
978-1-4244-2342-2/08/$25.00 ©2008 IEEE.
Montree Siripruchyanun
1144
a)
Excessive use of the active and/or passive elements [8, 12-15, 17-22]. b) Require changing circuit topologies to achieve several functions [9-10, 13-15]. c) Lack of electronic adjustability [8, 12-15, 17-21]. d) Can not provide completely standard functions [8-9, 11, 13-14, 17-18, 20]. e) Can not provide functions both in voltage and current-modes with the same topology [11, 13, 15, 17].
This work is arranged to propose a new voltage/current– mode universal biquadratic filter, emphasizing on use of single CCCCTA. The features of proposed circuit are that: the proposed universal filter can provide completely standard functions both in voltage-mode and current-mode without changing circuit topology by appropriately selecting the input signals: the circuit description is very simple, it consists of 1 CCCCTA and 2 capacitors, which is suitable for fabricating in monolithic chip: the filter does not require any external resistor. In addition, the natural frequency and the bandwidth can be tuned electronically by adjusting the bias currents. Its performances are illustrated by PSPICE simulations, they show good agreement as mentioned. II.
⎛ 1 gm gm ⎞ + Vin 2 ⎜ s + ⎟ C1 C R C C 1 2 Rx ⎠ . ⎝ 1 x gm 1 s2 + s + C1 Rx C1C2 Rx
Vin1 s 2 + Vin 3 s VO =
I B1 I in1
Vin1
Basic Concept of CCCCTA The CCCCTA properties are similar to the conventional CCTA, except that the CCCCTA has finite input resistance Rx at the x input terminal. This parasitic resistance can be controlled by the bias current IB1 as shown in the following equation
o
y
CCCCTA z2 z1
Vin 2
CIRCUIT PRINCIPLE
I in 2
0 0 0 ⎤ ⎡Ix ⎤ ⎢ ⎥ 1 0 0 ⎥⎥ ⎢Vy ⎥ , 0 0 0 ⎥ ⎢Vz1 ⎥ ⎥⎢ ⎥ 0 ± g m 0 ⎦ ⎣⎢Vo ⎦⎥
Rx =
TABLE I.
THE
Vin1 , Vin 2
Vy
Vx
iy
ix
y x
CCCCTA z1
o
x
z2 iz 1
Vz 1
y
iz 2
Vz 2
Vin 3
Filter Responses BP
(2)
gmVz 1 io
AND
VALUE SELECTIONS FOR EACH
FILTER FUNCTION RESPONSE
VT I , gm = B 2 . 2 I B1 2VT
IB2
I in 3
C2
From Eq. (3), Vin1, Vin2 and Vin3 can be chosen as in Table I to obtain a standard function of the 2nd–order network. From Table I, it should be remarked that, in case of the BP, BR, AP and LP, the circuit condition: Rx=1/gm is required.
(1)
g m is the transconductance of the CCCCTA and VT is the thermal voltage. The symbol and the equivalent circuit of the CCCCTA are illustrated in Fig. 1(a) and (b), respectively.
I B1
IO
Figure 2. Proposed dual-mode universal filter
VO
where
Vo
Vin 3
A.
⎡ I y ⎤ ⎡0 ⎢ ⎥ ⎢ ⎢Vx ⎥ = ⎢ Rx ⎢I ⎥ ⎢1 ⎢ z1, z 2 ⎥ ⎢ ⎢⎣ I o ⎥⎦ ⎣ 0
IB2
x
C1
(3)
1 ix Rx
(Rx=1/gm)
HP
Input selections Vin1
Vin2
Vin3
0
0
1
1
0
0
BR
(Rx=1/gm)
1
1
-1
AP
(Rx=1/gm)
1
1
-2
LP
(Rx=1/gm)
0
1
-1
For current-mode case, where Vin1=Vin2=Vin3=0, straightforwardly analyzing the circuit in Fig. 2, the output current can be obtained as
o
I in1 s IO =
⎛ gm gm 1 1 + I in 2 − I in3 ⎜ s 2 + s + C1 Rx C1C2 Rx C1 Rx C1C2 Rx ⎝ gm 1 s2 + s + C1 Rx C1C2 Rx
⎞ ⎟ ⎠.
(4)
From Eq. (4), the magnitudes of input currents Iin1, Iin2 and Iin3 can be chosen as in Table II to obtain a standard function of the network. The circuit of digital selection can be seen in [23]. From Eqs. (3)-(4), for dual-mode, the natural frequency (ω0) and quality factor (Q0) of each filter response can be expressed as
z1 z2 iz 1 = iz 2 = ix
Figure 1. CCCCTA (a) Symbol (b) Equivalent circuit
B. Proposed Dual-Mode Universal Biquad Filter The proposed dual-mode universal filter is shown in Fig. 2, where IB1 and IB2 are input bias currents of CCCCTA. They are used to control the corresponding parasitic resistance and transconductance gain. For voltage-mode case, where Iin1=Iin2=Iin3=0, straightforwardly analyzing the filter in Fig. 2, the output voltage can be obtained as
ω0 =
gm C1 g m , Q0 = . C1C2 Rx C2 Rx
(5)
Substituting intrinsic resistance and transconductance as depicted in Eq. (2), it yields
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ω0 =
1 VT
I B1 I B 2 C1 I B 2 , Q0 = . C1C2 C2 I B1
(6)
From Eq. (6), by maintaining the ratio IB1 and IB2 to be constant, it can be remarked that the natural frequency can be adjusted by IB1 and IB2 without affecting the quality factor. In addition, bandwidth (BW) of the system can be expressed by BW =
ω0
=
Q0
2 I B1 . C1VT
(7)
We found that the bandwidth can be linearly controlled by IB1. Moreover, it can be seen that the natural frequency can be also adjusted orthogonally from the bandwidth by varying IB2. TABLE II.
THE
I in1 , I in 2
AND
I in3
Iin1 1 1 1 2 0
Q
Input selections Iin2 0 1 0 0 1
Iin3 0 1 1 1 0
I B1 Q1
(10)
= −1
Therefore, all the active and passive sensitivities are equal or less than unity in magnitude. D. Non-ideal case For non-ideal case, the I z and I o of CCCCTA can be respectively characterized by Vx = β Vy + I x Rx , I z1 = α1 I x , I z 2 = α 2 I x , I o = γ g mVz1 , (11)
α , γ and β are transferred error values deviated from one. In the case of non-idea and reanalysis of proposed filter circuit in Fig. 2, it respectively yields output voltage and current as ⎛ β α βγ g m + Vin 2 ⎜ s + 1 C1 ⎝ C1 Rx C1C2 Rx αγg 1 + 1 m s2 + s C1 Rx C1C2 Rx
Vin1 s 2 + Vin 3 s VO =
I in1 s IO =
α2 C1 Rx
+ I in 2
γ gm
⎞ ⎟ ⎠,
⎛ g mα1α 2γ αα γg 1 − I in 3 ⎜ s 2 + s + 1 2 m C1C2 Rx C1 Rx C1C2 Rx ⎝ α1γ g m 1 2 + s +s C1 Rx C1C2 Rx
In this case, the ω0 and Q0 are changed to
Q8
Q9
Q6
Q7
Q14 Q15
z1
Q4
Q3
Q14
Q5
VCC
Q16
o
z2
x
III.
(8)
= 1; S
=S
Q2
Q13
Q15
Q23
IB2
VEE
Figure 3. Internal construction of CCCCTA
(9)
S
11
y
1 1 S IQB02 = SCQ10 = ; S IQB01 = SCQ20 = − 2 2, BW C1
Q12
Q
10
1 1 S IωB01 , I B 2 = , SCω10,C2 = − , SVωT0 = −1, 2 2
BW VT
α1γ C1 Rx g m
VALUE SELECTIONS FOR EACH
C. Circuit Sensitivities The sensitivities of the proposed circuit can be found as
BW I B1
, Q0 =
, (14) C1C2 Rx C2 while BW is still equal to Eq. (7). Actually, these deviations are very small and can be ignored. Practically, from Eqs. (1114), α, γ and β originate from intrinsic resistances and stray capacitances in the active elements. These errors affect the sensitivity to temperature and high frequency response of the proposed circuit. From Eq. (14), it is found that the pole frequency and quality factor depend on the temperature and frequency variations, then the CCCCTA should be carefully designed to achieve these errors as low as possible.
FILTER FUNCTION RESPONSE
Filter Responses IO BP HP BR AP LP
α1γ g m
ω0 =
(12)
SIMULATION RESULTS
To prove the performances of the proposed circuit, the PSPICE simulation program was used. The PNP and NPN transistors employed in the proposed circuit were simulated by respectively using the parameters of the PR200N and NR200N bipolar transistors of ALA400 transistor array from AT&T [24]. Fig. 3 depicts schematic description of the CCCCTA used in the simulations. The circuit was biased with ±1.5V supply voltages. C1=C2=1nF and IB1=54µA, IB2=200µA are chosen. It yields the natural frequency of 540.75kHz, while calculated value of this parameter from Eq. (7) is 612.45kHz. The results shown in Fig. 4 are the gain and phase responses of the proposed biquad filter in voltage-mode obtained from Fig. 2. There are seen that the proposed filter in voltage-mode can provide low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on selection as shown in Table I, without modifying circuit topology. The gain and phase responses of the proposed biquad filter in current-mode are also investigated, which are similar to those of voltage-mode. Fig. 5 shows gain responses of current-mode band-pass function where IB1 and IB2 are equally set to keep the ratio to be constant and changed for several values. It is found that pole frequency can be adjusted without affecting the quality factor, as depicted in Eq. (6). Maximum power consumption is about 1.81mW. IV.
⎞ ⎟ ⎠ . (13)
CONCLUSIONS
The dual-mode universal biquadratic filter based on single CCCCTA has been presented. The advantages of the proposed circuit are that: it performs low-pass, high-pass, band-pass, band-reject and all-pass functions dependent on an appropriate selection of three signals in dual-mode: the quality factor and the pole frequency can be electronically controlled via input bias currents, it is easily modified to use in control systems using a microcontroller [3]. The circuit description comprises
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REFERENCES [1] [2]
[3] [4]
[5]
[6]
[7]
[8] [9] [10] [11]
[12]
[13]
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[18]
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A. S. Sedra, and K. C. Smith, Microelectronic circuits, 5th ed., Florida: Holt, Rinehart and Winston, 2003. M. A. Ibrahim, S. Minaei, and H. A. Kuntman, “A 22.5 MHz currentmode KHN-biquad using differential voltage current conveyor and grounded passive elements,” Int. J. Electron. Commun. (AEU), vol. 59, pp. 311-318, 2005. C. Toumazou, F. J. Lidgey, and D. G. Haigh, Analogue IC design: the current-mode approach, London: Peter Peregrinus, 1990. D. R. Bhaskar, V. K. Sharma, M, Monis, and S. M. I. Rizvi, “New current-mode universal biquad filter,” Microelec. Journal, vol. 30, pp. 837-839, 1999. R. Prokop, V. Musil, “New modern circuit block CCTA and some its applications,” Proceeding of ET'2005, Book 5. Sofia: TU Sofia, pp. 9398, 2005. M. Siripruchyanun and W. Jaikla, “Current controlled current conveyor transconductance amplifier (CCCCTA): a building block for analog signal processing,” Proceeding of ISCIT 2007, Sydney, Australia, pp. 1072-1075, 2007. M. Siripruchyanun, M. Phattanasak and W. Jaikla, “Current Controlled Current Conveyor Transconductance Amplifier (CCCCTA): A Building Block for Analog Signal Processing,” 30th Electrical Engineering Conference (EECON-30), pp. 897-900, 2007. N. A. Shah and M. A. Malik, “Multifunction mixed-mode filter using FTFNs,” Analog ICs and Signal Processing, vol. 47, pp. 339-343, 2006. J. WU and E. I. EL-Masry, “Universal voltage- and current-mode OTAs based biquads,” Int. J. Electronics, vol.85, pp. 553-560, 1998. D. R. Bhaskar, R. K. Sharma, A. K. Singh, R. Senani, “New Dualmode Biquads Using OTAs,” Frequenz, vol. 60, pp. 246-252, 2006. D. R. Bhaskar, A. K. Singh, R. K. Sharma and R. Senani, “New OTAC universal current-mode/trans-admittance biquads,” IEICE Electron. Express, vol. 2, pp.8-13, 2005. N. Pandey, S. K. Paul, A. Bhattacharyya and S. B. Jain, “A new mixed mode biquad using reduced number of active and passive elements,” IEICE Electron. Express, vol. 3, pp.115-121, 2006. C. L. Hou, C. C. Huang, Y. S. Lan, J. J. Shaw and C. M. Chang, “Current and voltage-mode universal biquads using a single currentfeedback amplifier,” Int. J. Electronics, vol. 86, pp. 929-932, 1999. N. A. Shah and M. A. Malik, “Voltage/current-mode universal filter using FTFN and CFA,” Analog ICs and Signal Processing, vol. 45, pp. 197-203, 2005. S. T. Liu and J. L. Lee, “Insensitive current/voltage-mode filters using FTFNs,” Electronics Letters, vol. 32, pp.1079 –1080, 1996. N. A. Shah and M. A. Malik, “Multifunction mixed-mode filter using FTFNs,” Analog ICs and Signal Processing, vol. 47, pp. 339-343, 2006. N. A. Shah S. Z. Iqbal and B. Parveen, “SITO high output impedance transadmittance filter using FTFNs,” Analog ICs and Signal Processing, vol. 40, pp. 87-89, 2004. C. L. Hou and C. C. Lin, “A filter with three voltage-inputs and one voltage-output and one current-output using current Conveyors,” Tamkang Journal of Sci. and Eng., vol. 7, pp. 145-148, 2004. N. Pandey, S. K. Paul, A. Bhattacharyya and S. B. Jain, “A new mixed mode biquad using reduced number of active and passive elements,” IEICE Electron. Express, vol. 3, pp.115-121, 2006. A. Toker, O. ÇiÇekoglu, S. Özcan and H. Kuntman, “High output impedance transadmittance type continuous time multifunction fillter with minimum active elements,” Int. J. Electronics, vol.88, pp. 10851091, 2001. M. T. Abuelma'atti and A. Bentrcia, “A novel mixed-mode CCII-based filter,” Active and Passive Electronic Components, vol. 27, pp. 197205, 2004.
[22] M. T. Abuelma'atti, “A novel mixed-mode current-controlled currentconveyor-based filter,” Active and Passive Electronic Components, vol. 26, pp. 185-191, 2003. [23] W. Tangsrirat, “Low-voltage digitally programmable current-mode universal biquadratic filter,” Int. J. Electron Commun (AEU), Available online 26 April 2007. [24] D. R. Frey, “Log-domain filtering: an approach to current-mode filtering,” IEE Proc. Circuit Devices, vol. 140, pp. 406-416, 1993.
(a)
(b)
(c)
(d)
(e)
Figure 4. Gain and phase responses of the biquad filter in voltage-mode for (a) LP (b) HP (c) BP (d) BR (e) AP
Gain (dB)
only 1 CCCCTA and 2 capacitors. With mentioned features, it is very suitable to realize the proposed circuit in monolithic chip to use in battery-powered, portable electronic equipments such as wireless communication system devices.
Figure 5. Current-mode band-pass responses for different values of IB1 and IB2
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