Current-mode active-only universal filter NOTE - Semantic Scholar
Indian Journal of Pure & Applied Physics Vol. 41, July 2003, pp. 578-580
NOTE Current-mode active-only universal filter N A Shah & S Z Iqbal Department of Electronics & Instrumentation Technology. University of Kashmir, Srinagar 190006 Email:[email protected] Received 30 January 2003; revised 8 April 2003; accepted 25 April 2003 A new current-mode active-only universal filter based on and employing two OA's and three DOOT As is presented. The circuit is capable of realizing all the fi ve generic filter characteristics viz. Lowpass, bandpass, highpass, notch and all pass without changing the circuit topology or nature of components, or additional component besides, no component matching conditions is required. The filter parameters Ole. and Q are electronically tunable in an orthogonal manner through separate transconductances of OT As. The circuit has low sensitivity performance and is ideal for production in Ie form as it is devoid of external passive components.
[Keywords: Active-only High frequency operations]
filters, Filter circuits,
A great deal of research has been carried out to construct filter circuits which are either active-R', active-C'", or active-RC'" type, and quite a good number of such filters have been reported in the literature. Active-only filters utilizing the finite and complex gain nature of internally compensated OAs (ICOA) are suitable for high frequency operations. Moreover, OTAs provide highly linear electronic tunability and wide tunable range of their transconductance gain. However, very little attention has been paid towards developing filter circuits, which are active-only in nature. Activeonly filters have the advantages of integrability on a single chip, using either bipolar or CMOS technology. The active-only current-mode universal filters reported in the literature have the following disadvantages: (i) need matching conditions to be satisfied to realize" different filtering functions and,
thus, requires proportional block"!", and/or (ii) have three inputs and employ four OT As with single output and one OTA with four outputs, which is prohibitively a large number". In this paper, a new filter configuration, employing only active components viz. two OA's and three DO-OTAs is introduced. The circuit realizes three filter functions HP, BP and LP, simultaneously, without any change to be induced in the circuit topology or nature of components. The response characteristic for AP is realized by connecting the output currents IHP, -/BP , and ILP. and for notch is obtained by connecting IHP and ILP. Thus, AP and notch signals are realized without modifying the architecture of the circuit or using additional components, besides no component matching condition is required. The filter performance parameter ~) can be tuned through the transconductance gain gl and/or g, and then Q can be tuned through g2, without affecting ~.. Thus, sequential tunability of filter characteristics has been achieved. The distinct advantage of proposed circuit is that, it has only one input, unlike some of the previously reported circuits having many. The additional advantage of the circuit is that, the output currents are available at high impedance, thereby facilitating cascading to implement higher order filters without incorporating buffers. Circuit Description The proposed filter employing OA's and OTA's is shown in Fig. I. Using the complex gain nature of OA given by Ai(s) = Bi/s, where Bi is the gain band-width product of ith OA, the transfer output currents are as:
=
THP (/IIN= S2/ (s2+sB,g/g,+B,B:g,/g,) TBrl/IIN
TLP
= sB,(g/g,)/
= I/IIN=
(s2+sB,gigl+B,B2g/g,)
BIB2g/g/(S2+sBlg/gl+BIB2g/gl)
... ( 1) ... (2) ... (3)
The all-pass response characteristics is obtained by adding output currents iHP, -/BP and ILl' and is given by: TAP= iHP-/BP+/LP= (S2_ sli.g-Jg, +
NOTES
579
Fig. I -eM active-only universal filter
,.
0
!f
~ -s .....,
f
-9 -10
I
11 -tl
ti -JO u
-25
~
-~ lei004
J(DJ
leftm
Jei006
mqueucy (Hz) US 100
~
-8
j\
7l
'-" ~
••
j
p.,
1\\'-.
2S 0 .:.B
-~ leftm
lei004
110}
Fig. 2 -
Notch response of Fig. I
... (6)
... (4) Similarly, by connecting the output terminals IHP and Ill' notch response characteristics results for which the transfer function is given by: TN=/HP+/LP = (5" +
The filter given by:
performance
factors
~J
and
lrfIDS
Q are
Q
=
lIg2-Y(B2g\g,lB\)
... (7)
It is clear from Eqs (6) and (7) that, COt) and Q are electronically tunable through bias current of OT As (gi=1B/2 VT). To achieve non-interactive tuning, COt) is initially tuned through g\ and/or g3 and then Q is tuned
580
INDIAN
J PURE & APPL PHYS, VOL 41, JULY 2003
through g2' The active and passive sensitivities of this universal filter are:
requiring buffer. References Tsukutani Takao, Ishida Masaru Electron, 78 (1995) 1119.
all of which are no more than unity. Simulation Results - The notch response of the proposed circuit with at, resonance frequency 100 KHz and Q=I was simulated using PSPICE. The OA LM 741 with Bi =.21t(1.5xI06) rad/see and CA 3080 macro model" was used. The notch response of the filter is depicted in Fig. 2. Conclusion A new CM active-only filter realizing all the five generic filter functions is presented. Being without external passive components, the circuit is ideally suited' for IC form of construction. The filter characteristics (On and Q are electronically adjustable through separate transeonductances in a sequential mode. The circuit has low sensitivity performance contributing to its reliability. The circuit can be cascaded for higher filter-order realization, without
& Fukui Yutaka, Int .I
2
Wu lie & El-Masry Ezz I, lilt .I Electron, 85 (1998) 553.
3
Tsukutani Takao, Ishida Masaru, Tsuiki Sumio & Fukui Yutaka, lnt J Electron, 80 (1996) 533.
4
Sun Yichuang, Electron Lett, 34 (1998) 14~9.
5
Sun Yichuang & Filder 1 K, 11/1.1 Electron, 81 (1996) 95.
6
Chang Chan-Ming, IEEE Trans Circuits S)wt-lI, 44 (1997) 956.
7
Moniri Mansour & AI Hashimi Bashir, lilt .I Electron, 83 (1997),37.
8
Abuelma'atti M T & Khan M H, Electron Lett , 31 (J 995) 2160.
9
Tsukutani Takao, Higashimura Masami, Sumi Yasuaki & Fukui Yutaka, lllt./ Electron, 87 (2000) 307.
10 Tsukutani T, Ishadi M, Tsuiki S & Fukui Y, Electron Left, 32 (1996) 197. 11 Abuelma'atti M T & Alzaher H A, Electron Left, 3.3 (1997) 281. 12 Wu
r. i«: Electron,
76 (1994) I J 15. .
,'.
NOTE Current-mode active-only universal filter N A Shah & S Z Iqbal Department of Electronics & Instrumentation Technology. University of Kashmir, Srinagar 190006 Email:[email protected] Received 30 January 2003; revised 8 April 2003; accepted 25 April 2003 A new current-mode active-only universal filter based on and employing two OA's and three DOOT As is presented. The circuit is capable of realizing all the fi ve generic filter characteristics viz. Lowpass, bandpass, highpass, notch and all pass without changing the circuit topology or nature of components, or additional component besides, no component matching conditions is required. The filter parameters Ole. and Q are electronically tunable in an orthogonal manner through separate transconductances of OT As. The circuit has low sensitivity performance and is ideal for production in Ie form as it is devoid of external passive components.
[Keywords: Active-only High frequency operations]
filters, Filter circuits,
A great deal of research has been carried out to construct filter circuits which are either active-R', active-C'", or active-RC'" type, and quite a good number of such filters have been reported in the literature. Active-only filters utilizing the finite and complex gain nature of internally compensated OAs (ICOA) are suitable for high frequency operations. Moreover, OTAs provide highly linear electronic tunability and wide tunable range of their transconductance gain. However, very little attention has been paid towards developing filter circuits, which are active-only in nature. Activeonly filters have the advantages of integrability on a single chip, using either bipolar or CMOS technology. The active-only current-mode universal filters reported in the literature have the following disadvantages: (i) need matching conditions to be satisfied to realize" different filtering functions and,
thus, requires proportional block"!", and/or (ii) have three inputs and employ four OT As with single output and one OTA with four outputs, which is prohibitively a large number". In this paper, a new filter configuration, employing only active components viz. two OA's and three DO-OTAs is introduced. The circuit realizes three filter functions HP, BP and LP, simultaneously, without any change to be induced in the circuit topology or nature of components. The response characteristic for AP is realized by connecting the output currents IHP, -/BP , and ILP. and for notch is obtained by connecting IHP and ILP. Thus, AP and notch signals are realized without modifying the architecture of the circuit or using additional components, besides no component matching condition is required. The filter performance parameter ~) can be tuned through the transconductance gain gl and/or g, and then Q can be tuned through g2, without affecting ~.. Thus, sequential tunability of filter characteristics has been achieved. The distinct advantage of proposed circuit is that, it has only one input, unlike some of the previously reported circuits having many. The additional advantage of the circuit is that, the output currents are available at high impedance, thereby facilitating cascading to implement higher order filters without incorporating buffers. Circuit Description The proposed filter employing OA's and OTA's is shown in Fig. I. Using the complex gain nature of OA given by Ai(s) = Bi/s, where Bi is the gain band-width product of ith OA, the transfer output currents are as:
=
THP (/IIN= S2/ (s2+sB,g/g,+B,B:g,/g,) TBrl/IIN
TLP
= sB,(g/g,)/
= I/IIN=
(s2+sB,gigl+B,B2g/g,)
BIB2g/g/(S2+sBlg/gl+BIB2g/gl)
... ( 1) ... (2) ... (3)
The all-pass response characteristics is obtained by adding output currents iHP, -/BP and ILl' and is given by: TAP= iHP-/BP+/LP= (S2_ sli.g-Jg, +
NOTES
579
Fig. I -eM active-only universal filter
,.
0
!f
~ -s .....,
f
-9 -10
I
11 -tl
ti -JO u
-25
~
-~ lei004
J(DJ
leftm
Jei006
mqueucy (Hz) US 100
~
-8
j\
7l
'-" ~
••
j
p.,
1\\'-.
2S 0 .:.B
-~ leftm
lei004
110}
Fig. 2 -
Notch response of Fig. I
... (6)
... (4) Similarly, by connecting the output terminals IHP and Ill' notch response characteristics results for which the transfer function is given by: TN=/HP+/LP = (5" +
The filter given by:
performance
factors
~J
and
lrfIDS
Q are
Q
=
lIg2-Y(B2g\g,lB\)
... (7)
It is clear from Eqs (6) and (7) that, COt) and Q are electronically tunable through bias current of OT As (gi=1B/2 VT). To achieve non-interactive tuning, COt) is initially tuned through g\ and/or g3 and then Q is tuned
580
INDIAN
J PURE & APPL PHYS, VOL 41, JULY 2003
through g2' The active and passive sensitivities of this universal filter are:
requiring buffer. References Tsukutani Takao, Ishida Masaru Electron, 78 (1995) 1119.
all of which are no more than unity. Simulation Results - The notch response of the proposed circuit with at, resonance frequency 100 KHz and Q=I was simulated using PSPICE. The OA LM 741 with Bi =.21t(1.5xI06) rad/see and CA 3080 macro model" was used. The notch response of the filter is depicted in Fig. 2. Conclusion A new CM active-only filter realizing all the five generic filter functions is presented. Being without external passive components, the circuit is ideally suited' for IC form of construction. The filter characteristics (On and Q are electronically adjustable through separate transeonductances in a sequential mode. The circuit has low sensitivity performance contributing to its reliability. The circuit can be cascaded for higher filter-order realization, without
& Fukui Yutaka, Int .I
2
Wu lie & El-Masry Ezz I, lilt .I Electron, 85 (1998) 553.
3
Tsukutani Takao, Ishida Masaru, Tsuiki Sumio & Fukui Yutaka, lnt J Electron, 80 (1996) 533.
4
Sun Yichuang, Electron Lett, 34 (1998) 14~9.
5
Sun Yichuang & Filder 1 K, 11/1.1 Electron, 81 (1996) 95.
6
Chang Chan-Ming, IEEE Trans Circuits S)wt-lI, 44 (1997) 956.
7
Moniri Mansour & AI Hashimi Bashir, lilt .I Electron, 83 (1997),37.
8
Abuelma'atti M T & Khan M H, Electron Lett , 31 (J 995) 2160.
9
Tsukutani Takao, Higashimura Masami, Sumi Yasuaki & Fukui Yutaka, lllt./ Electron, 87 (2000) 307.
10 Tsukutani T, Ishadi M, Tsuiki S & Fukui Y, Electron Left, 32 (1996) 197. 11 Abuelma'atti M T & Alzaher H A, Electron Left, 3.3 (1997) 281. 12 Wu
r. i«: Electron,
76 (1994) I J 15. .
,'.
