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Practical Implementation of CCTA Based on

Commercial CCII and OTA

Winai Jaikla1 Phamorn Silapan2 Chaiyan Chanapromma3 and Montree Siripruchyanun3

1 Electric and Electronic Program, Faculty of Industrial Technology,

Suan Sunandha Rajabhat University, Dusit, Bangkok, 10300, THAILAND

Tel: +66-2-243-2240 Ext. 317, Fax: +66-2-241-5935, E-mail: winai.ja@ssru.ac.th

2 Electric and Industrial Program, Faculty of Industrial Technology,

Uttaradit Rajabhat University, Muang, Uttaradit, 53000, THAILAND Email: phamorn@mail.uru.ac.th

3 Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut’s University of

Technology North Bangkok, Bangsue, Bangkok, 10800, THAILAND Tel: +66-2- 913-2500 Ext. 3328 Fax. +66-2-587-8255

Email: chaiyanc@kmutnb.ac.th, mts@kmutnb.ac.th

Abstract- This article presents a basic current-mode

building block for analog signal processing, namely current

conveyor transconductance amplifier (CCTA) using the

commercially available ICs. The performances are examined

through PSPICE simulations and experiment, displaying

usabilities of the new active element. The description includes

some examples as a voltage-mode universal biquad filter, a

grounded inductance, a current-mode multiplier and oscillator.

They occupy only a single CCTA.

I.

INTRODUCTION

In the last decade, there has been much effort to reduce

the supply voltage of electronic circuits. This is due to the

demand for portable and battery-powered equipment. Since

a low-voltage operating circuit becomes necessary, the

current–mode technique is ideally suited for this purpose,

more so than voltage-mode. Consequently, there is a

growing interest in synthesizing current-mode circuits

because of their many 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 [3], current differencing buffered

amplifier (CDBA) [4], current feedback amplifier (CFA) [5-

7], and current differencing transconductance amplifier

(CDTA) [8] have been introduced in response to these

demands.

Recently, a reported 5-terminals active element, namely

the current conveyor transconductance amplifier (CCTA)

[9], seems to be a versatile component in the realization of a

class of analog signal processing circuits, especially analog

frequency filters [9-11]. It is supposed for usage mostly in

current-mode circuits, but it is also a choice in case of

voltage mode and/or hybrid (voltage-current) circuits (e.g.

V/I converters). In addition, it can also adjust the output

current gain. However, from our investigations, it is seen

that the CCTA has a third-generation current conveyor

(CCIII) as its input stage which has less flexibility for

applications than a second-generation current conveyor

(CCII). Moreover, the mentioned CCTA is implemented by

connection of CMOS transistors which is not easy to really

experiment. Until now, the practical implementation of

CCTA is not achieved yet.

The aim of this paper is to propose the implementation of

CCTA by using the commercially available ICs, which are

AD844 (CCII) and LM13600N (OTA). The performances of

proposed CCTA are proved by experiment and PSPICE

simulations, they show good agreement as mentioned. The

application examples as a voltage-mode universal biquad

filter, a grounded inductance simulator, a current-mode

multiplier and oscillator are included.

II. CIRCUIT CONFIGURATION

A. Basic Concept of CCTA

The properties of CCTA can be shown in the following

equation

00

01

10

00

o

I

??

?

??

where

0

0

0

0

0

0

0

yx

y

x

zz

m

o

I

V

I

I

V

V

V

g

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

, (1)

2

B

m

T

I

V

g

?

. (2)

T

V is the thermal voltage. The symbol and equivalent

circuit of the CCCCTA are illustrated in Fig. 1(a) and (b),

respectively.

I

B

y

x

z

o

CCTA

yi

xi

zi

oi ?

y

V

x

V

z V

o

V

1

y

x

o

z

xi

xi

mZ

g V

?

(a) (b)

Figure 1. (a) CCTA (b) Equivalent circuit.

zv

yv

xv

yi

xi

zi

y

x

z

OTA

?

?

BI

13600

LM?

844

AD

CCII

oi

ov

Figure 2. Implementaiton of CCTA based on commercially available ICs.

2008 International Symposium on Intelligent Signal

Processing and Communication Systems (ISPACS2008)

Swissôtel Le Concorde,Bangkok,Thailand

978-1-4244-2565-5/08/$25.00 ©2008 IEEE

Page 2

B. Proposed CCTA

The implementation of CCTA is shown in Fig. (2). It

consists of two principal blocks: a second generation current

conveyor (AD844) as input stage and a transconductance

amplifier (LM13600N) as

transconductance can be adjusted by input bias current of

the LM13600N.

III. SIMULATION RESULT

To prove the performances of the proposed CCTA, the

PSPICE simulation program was used. The CCTA were

implemented using AD844 and LM13600N as illustrated in

Fig. 2. The circuit was biased with ±10V supply voltages.

Fig. 3 displays the DC transfer characteristics of the

proposed CCTA. It is seen to be linear when

88.

x

mAImA

???

The bandwidths of output terminals are

shown in Fig. 4. The

/,/,/

zxxyox

IIV VII , and

/

o

IV are respectively located at

1.48GHz, 61.09MHz, 15.12MHz, and 15.06MHz.

8.0

output stage. The

3dB

?

bandwidths of

y

Ix(mA)

-10 -8-6-4-202468 10

-8.0

-4.0

0

4.0

Iz(mA)

Figure 3. DC transfer characteristic of the CCTA.

Gain (dB)

(a)

Frequency (Hz)

(b)

1.0k 3.0k 10k30k100k 300k1.0M 3.0M 10M 30M100M

-20

-10

0

5

IO/IX

IO/VY

Rx=Rz=1k?

IB=50μA

(f-3dB=15.12MHz)

(f-3dB=15.06MHz)

Figure 4. Frequency responses at output terminals.

IV. APPLICATION EXAMPLES AND RESULTS

A. Sinusoidal Oscillator

The first application of proposed CCTA is an oscillator,

shown in Fig. 5. It consists of only single CCTA, 1 resistor

and 2 grounded capacitors. Considering the circuit in Fig. 5,

and using the CCTA properties, yields the characteristic

equation of this circuit to be

?

12

x

s C C Rs C

?

From Eq. (3), it is seen that the proposed circuit can be set to be

an oscillator if

?

2

12

0

m

Cg

???

. (3)

Eq. (4) is called the condition of oscillation, thus the

characteristic equation of the system becomes

g

s

C C R

From Eq. (5), the oscillation frequency of this system can be

obtained as follows

g

C C R

It can be seen that, from Eq. (6), the oscillation frequency (

can be controlled by the bias current. The confirmed

performance of the oscillator can be seen in Fig. 6, showing

the simulated response of the oscillator. The total harmonic

distortion (THD) is about 5.75%. The experimental response

is illustrated in Fig. 7.

12

CC

?

. (4)

2

12

0

m

x

??

. (5)

0

1212

2

m

B

xTx

I

V C C R

? ??

. (6)

0

? )

B I

x

y

z

o

CCTA

1

C

2

C

O

V

x

R

Figure 5. Oscillator based on the CCTA.

Time (ms)

00.10.2 0.30.4 0.5 0.60.70.8 0.91.0

-8.0

-4.0

0

4.0

8.0

C1=1nF

C2=1.07nF

Rx=1k?

IB=100μA

Figure 6. Simulated response of the oscillator in Fig. 5.

Figure 7. Experimental response of the oscillator in Fig. 5.

B. Grounded Inductance Simulator

The grounded inductance simulator based on the CCTA is

shown in Fig. 8. It employs only single CCTA and a

grounded capacitor. From routine analysis and by using the

CCTA properties, the input impedance of the circuit can be

written to be

V

Z

I

From Eq. (7), it is obvious that the circuit shown in Fig. 10

performs a grounded inductance with a value

inx

in

inm

sCR

g

??

. (7)

Page 3

2

T

I

x

eq

B

V CR

L

?

. (8)

From Eq. (8), the inductance value

electronically by

simulator relative to frequency (compared to ideal inductor)

are also shown in Fig. 9. Fig. 10 shows impedance values

relative to frequency of the simulator with different IB.

eq

L can be adjusted

BI . The impedance and phase of the

B I

y

x

z

o

?

CCTA

C

in I

in

V

x R

Figure 8. Grounded inductance simulator based on the CCTA.

Frequency (Hz)

100 1.0k10k 100k 1.0M10M

0d

25d

50d

75d

100d

1.0

100

10k

1.0M

100m

Ideal

Simulated

Impedance

Phase

Rx=0.5k?

IB=100μA

Figure 9. The impedance and phase relative to frequency of the grounded

inductance simulator.

Figure 10. The impedance values relative to frequency of the simulators

with different IB.

B

I

x

y

z

CCTA

o

A I

oI

x R

Figure 11. Current-mode multiplier based on the CCTA.

C. Current-Mode Multiplier

The multiplier based on the CCTA is shown in Fig. 11. It

employs only a single CCTA. From routine analysis using

the CCTA properties, we will get output current IO to be

I I

I

V R

From Eq. (9), it is seen that IO is a result of multiplying of IA

and IB. Due to being a positive value of IB, the proposed

circuit can be a 2 quadrant multiplier. In addition, if IA is an

input current, the proposed circuit can work as a current

amplifier, while the magnitude of output current can be

controlled electronically by IB. Fig. 12 shows the DC

4

A B

O

Tx

?

. (9)

response characteristics of multiplication. Fig. 13 shows the

transient responses of multiplication, where

set to be a sinusoidal signal of 150

triangular signal 50

P

A

?

at 10kHz frequency.

A I and

BI were

P P

A

?

? at 100kHz and a

IO(μA)

Figure 12. Static characteristics of the multiplier.

IO(μA)

Figure 13. Transient responses of the multiplier.

D. Voltage-Mode Universal filter

The voltage-mode universal filter based on CCTA is shown

in Fig. 14. By routine analysis of the circuit in Fig. 14, the

output voltage can be obtained to be

2

112

2

12

s C C

?

TABLE I

The

in

V

2

in

V

3

in

V

Filter Responses

V

BP

HP

LP

BR

AP

From Eq. (10), Vin1, Vin2 and Vin3 can be chosen as in Table I

to obtain a standard function of the 2nd–order network. The

pole frequency (?0) and quality factor (Q0) of each filter

response can be expressed to be

g

C C R

It is obviously found that, from Eq. (11), the quality factor

can be adjusted by R1 without affecting the pole frequency.

Moreover, the pole frequency can be electronically

controlled by IB. The bandwidth (BW) of the system can be

expressed by

?

?

221

?

3

21

inin inxm

O

xm

V s C CV sC G

sC G

V G g

G g

V

??

?

. (10)

1,

and value selections for each filter function response

Input

V

1

0

0

0

-1

O

1

in

0

1

0

1

1

V

2

in

3

in

0

0

1

1

1

V

1

001

122

,

mm

xx

C g

C R

QR

? ??

. (11)

0

011

1

BW

QRC

?

. (12)

We found that the bandwidth can be linearly controlled by

R1. The sensitivities of the proposed circuit can be found to

be

Page 4

000

2

0

x

1

1

2

?

1

2

;,

m

gCCR

SSSS

????

???? ?

(13)

000

x

0

2

0

11

1

2

S

1

2

;;1

m

Q

g

Q

C

Q

R

Q

C

Q

R

SSSSS

?? ? ?? , (14)

Therefore, all the active and passive sensitivities are equal

or less than unity in magnitude.

V

11

1

BW

R

BW

C

S

? ? ? . (15)

B

I

y

x

o

?

CCTA

z

2

C

2

in

V

O

V

1

C

1

in

3

in

V

1 R

x

R

Figure 14. Voltage-mode universal biquad filter based on the CCTA.

Gain (dB)

Phase

(a)

Gain (dB)

Phase

(b)

Frequency (Hz)

(c)

3.0k10k 30k100k 300k1.0M3.0M10M

-200d

-100d

0d

-80

-40

0

40

Gain

Phase

Gain (dB)

Phase

Frequency (Hz)

(d)

3.0k 10k30k100k 300k1.0M3.0M10M

-100d

0d

100d

-50

-25

0

Gain

Phase

Phase

Gain (dB)

Frequency (Hz)

(e)

3.0k10k30k100k300k1.0M3.0M 10M

-400d

-200d

0d

-10

-5

0

5

10

Gain

Phase

Figure 15. Gain and phase responses of the biquad filter in current-mode

for (a) BP (b) HP (c) LP (d) BR (e) AP.

The results shown in Fig. 15 are the gain and phase

responses of the proposed biquad filter obtained from Fig.

14, where C1=C2=1nF, IB100μA and R1= Rx=1k?. The

figures show that the proposed filter 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. Fig. 16 display gain responses

of band-pass function, with different R1 values. They are

shown that the quality factor can be adjusted by R1 as

depicted in Eq. (11) without affecting the pole frequency

0

Frequency (Hz)

3.0k10k 30k100k 300k1.0M3.0M 10M

-50

-25

R1=0.5k?

R1=1k?

R1=2k?

Figure 16. Band-pass responses for different values of R1.

CONCLUSIONS

The building block, called the CCTA implemented by

using the commercially available ICs, has been introduced

via this paper. The usabilities have been proven by the

simulation, experiment and application examples. They

consume a few number of components, while electronic

controllability is still available, which differs from other

recently proposed elements. Our future work is to find more

applications of the CCTA, emphasizing the current-mode

signal processing circuits such as signal generator, rectifier,

etc.

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