Realization and Study of High Performance Voltage Mode Oscillator based on CCCCTA: A Building Block for Analog Signal Processing

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Realization and Study of High Performance Voltage Mode Oscillator based on CCCCTA: A Building Block for Analog Signal Processing Powered By Docstoc
					                                         (IJCSIS) International Journal of Computer Science and Information Security,
                                         Vol. 8, No. 9, December 2010




Realization and Study of High Performance Voltage Mode Oscillator based on
          CCCCTA: A Building Block for Analog Signal Processing

                         Deependra Pandey1 and Prof.(Dr.) L.K. Singh2
                  1
                      Asst. Professor, Dept. of ECE, Amity University, Lucknow
                      2
                        Director, IET, Dr. R. M. L. Avadh University, Faizabad

                                         ABSTRACT
At present there is a growing interest in designing current mode circuits. This attributed to their
large signal bandwidth, great linearity, wider dynamic range, simple circuitry and low power
consumption. The paper presents a basic current-mode 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 a current-mode signal processing, which is continually more
popular than a voltage one. The proposed element is realized in a CMOS technology and is
examined the performances through PSPICE simulations. The CCCCTA performs tuning over a
wide current range. In addition, some circuits for example as a current-mode universal biquad
filter and a grounded inductance occupy only single CCCCTA.
Keywords: Current Conveyors, CCCCTA, Current-mode circuits, Voltage Mode Oscillator

           1 INTRODUCTION                               the requirement more chip area. In addition,
                                                        the mentioned CCTA has a third-generation
 In the last decade, there has been much                current conveyor (CCIII) as its input stage
effort to reduce the supply voltage of                  which has less flexibility for applications
electronic circuits. This is due to the                 than a second-generation current conveyor
command for portable and battery-powered                (CCII). But the parasitic resistance at the
equipments. Since a low-voltage operating               input current port can be controlled by an
circuit becomes necessary, the current–mode             input bias current in CCCCTA. Even though
technique is ideally suited for this purpose            CCCCTA is implemented by employing
more than the voltage-mode one.                         CCCII and OTA, it is very convenient and
Current controlled current conveyor                     useful if the CCCCTA is realized in
transconductance amplifier (CCCCTA) is                  monolithic chip to compact the circuits and
the modified version of current conveyor                systems. The performances of the proposed
transconductance amplifier (CCTA). CCTA,                CCCCTA are illustrated by PSPICE
seems to be a versatile component in the                simulations, and they show good agreement
realization of a class of analog signal                 with the analysis.
processing circuits, especially analog
frequency filters. It is seen that the CCTA                  2 BASIC CONCEPT OF CCCCTA
cannot be controlled by the parasitic
resistance at the input port, so when it is             A5-terminals active element, namely current
used in some circuits, it must unavoidably              conveyor       transconductance      amplifier
require some external passive components,               (CCTA) , seems to be a versatile component
especially resistors. This makes it                     in the realization of a class of analog signal
inappropriate for IC implementation, due to             processing circuits.



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                                          (IJCSIS) International Journal of Computer Science and Information Security,
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However, it is seen that the CCTA can not                mixed translinear loop (M6–M9).The mixed
be controlled the parasitic resistance at input          loop is DC biased by using current mirrors
port so when it is used in some circuits, it             (M1–M3 and M10–M11). The output Z-
must unavoidably require some external                   terminal that generates the current from the
passive components, especially the resistors.            X-terminal is realized using transistors (M4–
This makes it not appropriate for IC                     M5 and M12–M13). The simplified
implementation due to occupying more chip                transconductance amplifier is realized using
area. The purpose of this paper is to design             transistors (M14–M17). The transconductance
and study a modified-version CCTA, which                 amplifier is DC biased by using current
is newly named current controlled current                mirror (M18-M19) and transconductance gain
conveyor      transconductance        amplifier          can be adjusted by IB2.
(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. The
performances of proposed CCCCTA are
illustrated by PSPICE simulations, they
show good agreement as mentioned.
CCCCTA properties are similar to the
conventional CCTA, except that the
CCCCTA has finite input resistance RX at
                                                               Fig.2: Proposed CMOS CCCCTA
the X-input terminal. This parasitic
resistance can be controlled by the bias
                                                         2.2CMOS CCCCTA Performance Results
current IB1. The symbol and the equivalent
circuit of the CCCCTA are illustrated in
                                                         PSPICE simulation on the CMOS
Fig.1(a) and (b), respectively.
                                                         implemented circuit of CCCCTA employed
                                                         the PMOS and NMOS transistors, using the
                                                         parameters of a 0.35µm TSMC CMOS
                                                         technology with ±1.5V supply voltages.
                                                         The aspect ratios of PMOS and NMOS
                                                         transistors are listed in Table 1.
                                                         Table 1: Dimensions of the MOS transistors
 Fig.1: (a) Symbol (b) Equivalent circuit                CMOS Transistors          W(µm)/L (µm)
                                                         M1-M5                     5/0.5
                                                         M6-M7                     4/0.5
2.1 Proposed CMOS Model of CCCCTA                        M8-M9                     2/0.5
                                                         M10-M13                   15/0.5
The proposed CCCCTA consists of two                      M14-M15 M18-M19 15/1.5
principal building blocks: a current                     M16-M17                   30/1.5
controlled second generation current
conveyor (CCCII) circuit and an operational              D.C. ANALYSIS
transconductance amplifier (OTA) circuit.
The proposed realization of the CCCCTA in                Fig.4 displays DC characteristics of the
a CMOS technology to achieve a wide-range                proposed CCCCTA, when IB1 = IB2 = 30 µA.
of frequency responses is shown in Fig. 2.               So it is clearly seen that it is linear in
The circuit implementation consists of the               −500mV<Vy <500mV.


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Fig.5 and Fig.6 displays DC characteristics             single CCCCTA                 and      two        grounded
of the proposed CCCCTA, when                            capacitors.
IB1=IB2=30µA. So it is clearly seen that it is
linear in −500µA<IX<500µA.

A.C. ANALYSIS
A.C. input signal is also applied at input
terminal and simulated bandwidths of output
terminals are shown in Fig.7. The −3 dB
cutoff frequencies of the current gains Iz/Ix
and Io/ Ix are, respectively, located at
835MHZ, 198 MHz, when IB1 =IB2 =50µA.
It has been found that the frequency
responses at O-terminal is narrower than
those at the Z-terminal, this is due to signal
transmission from the Z to O-terminal of
transconductance amplifier.
                                                                Fig. 3: VM oscillator based on the
TRANSIENT RESPONSE                                                        CCCCTA

PSPICE simulation is also carried out for               Design and Verifications
sinusoidal inputs of 100KHZ frequency.
These results also give a good agreement                Frequency response
between expected and experimental results.              The voltage-mode oscillator of Fig.3 is
These results also verify the basic Equation            verified using the model of PMOS and
of CCCTA in time domain in Fig. 8. The                  NMOS transistors. The parameters of a
THD was found low up to the high                        0.35µm TSMC CMOS technology with
frequency.                                              ±1.5V supply voltages have been used. To
                                                        prove the performance of the voltage-mode
3 VOLTAGE-MODE OSCILLATOR
                                                        oscillator, the PSPICE simulation program
Numerous oscillator circuits using different            used. C1 = C2 = 0.01nF, IB1 = 10µA, and IB2
types of current conveyors and passive                  = 330µA are chosen to obtain the pole
components have been reported. Whereas                  frequency of 3.77MHz. The waveforms and
most of the works reported were based on                fourier plots are shown in Fig.9. The T.H.D.
voltage mode outputs . Sinusoidal oscillators           of the proposed circuit at output is within
play an important role in instrumentation,              3%. The frequency of oscillation is found to
communication and signal processing                     vary from 0.6MHZ at IB2=10µA to
applications. Several of the already reported           4.25MHZ at IB2=500µA, which shows a
circuits exhibit the Quadrature outputs (with           wide variation in frequency for a variation in
90º phase shift, whereas some circuits                  IB2 and frequency of oscillation can be
provide multiphase outputs.                             independently controlled with the help of
                                                        IB2, without any change in condition of
Circuit Description                                     oscillation.
The voltage-mode oscillator based on
CCCCTA is shown in Fig.3. It consists of a



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                                  4 FIGURES

    500mV




       0V




-500mV
    -500mV                                     0V                                        500mV
         V(1)
                                               VY

                       Fig. 4: Vx vs Vy plot for CCCCTA


     500uA
O
U
T
P
U
T

C       0A
U
R
R
E
N
T
    -500uA
        -500uA                                  0A                                         500uA
             I(VZ)
                                                IX

                     Fig. 5: Output current variation with Ix




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            800uA
    O
    U
    T       500uA
    P
    U
    T

    C     0A
    U
    R
    R
    E
    N -500uA
    T

        -800uA
            -800uA             -400uA                    0A                    400uA                  800uA
                 I(VZ)
                                                         IX

                Fig.6: Output current variation with Ix showing IB1 independence


     20
C
U
R
R
E       0
N
T

G
A -20
I
N


    -40
                1.0KHz                  1.0MHz                           1.0GHz           100GHz
               DB(I(VZ1)/I(IX))
                                          Frequency

                                   Fig. 7: Current Gain in dB




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     100uA
                          Ix                  Iz


C
U
R
R
E       0A
N
T


                           Io

    -100uA
             0s               5us                    10us                      15us                   20us
                  I(IX)    I(R1)       I(VO)
                                                     Time

                                Fig. 8 Input/Output Current responses




    1.0V



V
O
L
T     0V
A
G
E



    -1.0V
       4.0us              4.4us            4.8us                 5.2us                 5.6us               6.0us
           V(2)
                                                         Time


                     Fig.9: Voltage output (VO1) of voltage-mode oscillator



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            5 CONCLUSIONS                               passive electronic components, No.4, pp.
                                                        219-227.
Current-mode circuits are undoubtedly the               [6] A. ÄU. Keskin, Dalibor Biolek, Erhan
most widely accepted operational devices in             Hancioglu and Viera Biolkova (2006)
continuous time and current mode signal                 ‘Current-mode KHN filter employing
processing. In addition a number of novel               current     differencing    transconductance
circuit functions and topologies have been              amplifiers,’AEU International Journal of
explored on a front of current mode                     Electronics and Communications, Vol. 60,
analogue circuits, opening up wider area of             No. 6, pp.443-446.
interest.The new building block, called as              [7] M. Siripruchyanum, W. Jaikla (2007)
CCCCTA, has been introduced via this                    ‘Realization of current controlled current
paper. The usabilities have been proven by              differencing transconductance amplifier
the simulation and application examples.                (CCCDTA) and its application,’ ECTI
They require few numbers of components                  electronics and communications, Vol. 5,
while electronic controllability is still               No.1.
available, which differs from the recently              [8] S. Maheshwari, I. A. Khan, and J.
proposed elements. This novel element is                Mohan (2006) “Grounded capacitor first-
very appropriate to realize in a                        order filters including canonical forms,”
commercially-purposed integrated circuit.               Journal of Circuits, Systems and Computers,
Our future work is to find more applications            vol. 15,no. 2, pp. 289–300.
of the CCCCTA, emphasizing on current-                  [9] S. Maheshwari and I. A. Khan, “Current
mode signal processing circuits such as                 controlled third order quadrature oscillator”,
multiplier/divider, rectifier, etc.                     IEE Proc. Circuits Devices and System, vol.
                                                        152, pp. 605-607, 2005.
              6 REFERENCES
[1] K. Smith and A. Sedra. (1968) ‘The                  [10] S. Maheshwari, “Electronically tunable
Current Conveyor-a new circuit building                 quadrature oscillator using translinear
block,’ IEEE Proc., vol. 56, pp. 1368-1369.             conveyors and grounded capacitors”, Active
[2] A. Sedra, K. C. Smith. (1970) ‘A second             and Passive Electronic Components (USA),
generation current conveyor and its                     vol. 26, pp. 193-196, 2003.
application’, IEE Trans. Circuit Theory, pp.
132-134.                                                [11] A. U. Keskin and D. Biolek, “Current
[3] Rajput , S. S., and Jamuar, S. S. (2004).           mode quadrature oscillator using Current
“Low Voltage, High Performance Current                  Differencing Transconductance Amplifier
Conveyors for Low Voltage Analog And                    (CDTA)”, IEE Proc.-Circuits Devices
Mixed       Mode       Signal      Processing           Systems, vol. 153, 2006.
applications”, Analog Integrated Circuits
and Signal Processing 41(1), 21–34.
[4] D. Biolek(2003) ‘CDTA Building block
for current-mode analog signal processing,’
Proceedings of the European conference on
circuit theory and design 2003 - ECCTD'03,
Krakow, Poland, pp. 397-400.
[5] S. Maheshwari, I.A. Khan (December
2004)        ‘Current-controlled      current
differencing        buffered        amplifier:
Implementation and applications’, Active



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