CDBA Based General Impedance Converter

Kevin Gajera

Department of Electronics and Communication

Delhi Technological University

New Delhi, India

Kdpatel621@gmail.com

Gautam Rathee

Department of Electronics and Communication

Delhi Technological University

New Delhi, India

ratheegautam@gmail.com

Abstract This paper presents new realization of GIC

using current differencing buffered amplifier. CDBA is

realized using CMOS. The presented topology can realize

resistance, inductance and frequency dependent negative

resistance (FDNR). Inductors are bulky and costly and

reducing the size of the inductors reduces the quality factor.

There is also a fundamental limitation of using inductor

that it cannot be suitable for the micro miniature structures

and integrated circuits applications. Because of these

limitations, inductors cannot be used in most of the analog

circuit applications. Hence, simulated inductors are used as

an alternative. The performance of the GIC is verified with

PSPICE. Finally, a first order band pass (BP) filter

configuration is proposed to show the performance and

usefulness of the circuit. The results from PSPICE

simulation are in remarkable agreement with expected

ones.

Keywords current differencing bufferd amplifier (CDBA),

general impedance converter(GIC), frequency dependent

negative resistance(FDNR), Bandpass, current mode.

I INTRODUCTION

GIC is realized using Op-Amp as an active element and is used

in active network synthesis of voltage transfer functions. The

GIC can also be used in realization of inductance and frequency

dependent negative resistance (FDNR). Inductor is the one of

the most important passive components used in all analog

circuits. But there are serious limitations in using it. Some of

them are:

Lessening the size of the inductor shrinks the quality factor.

The best achievable value of the quality factor with the inductor is 1000 since the large inductors are lossy. But even

higher values of 5,000 to 10,000 can be accomplished with the

capacitor.

At low frequencies, inductors are seldom used because the inductors are unwieldy.

As the inductors made of ferromagnetic materials which are nonlinear in nature, they create harmonic distortion if the

amplitude of the signal is large and direct currents are not

avoided.

Inductors have a tendency to act as miniature antennas, radiating as well as picking up electromagnetic waves. This can

result in unwanted noise and mixing of signals in circuits

containing inductors.

Recently, a new active current mode element, named, current

differencing buffered amplifier [1] (CDBA), has received much

attention in the electronics community. CMOS realization of

CDBA [2] is shown in fig 2.CDBA is free from many parasitic

capacitances and is suitable for low voltage operations. In

addition to the low voltage operations, popularity of current-

mode circuits can be attributed to some other features such as

larger dynamic range, low power consumption and higher

speeds. Realization of GIC using other active elements like

operational transresistance amplifier [3] (OTRA), current

conveyor has been done so far. In this paper, new topology for

GIC using three CDBA, four resistors and one capacitor is

reported. Some applications of topology are also presented.

II CIRUIT DESCRIPTION

CDBA is a four terminal device with two inputs and two

outputs. Circuit symbol of CDBA is shown in fig.1 and

behavior of component is characterized by following equations

-

According to the equations, current through Z terminal follows

the difference of current through P and N terminal and the

voltage of W terminal follows the voltage of Z terminal. P and

N terminal are internally grounded.

Figure 1(a) Circuit symbol of CDBA (b) Equivalent circuit of CDBA

III. APPLICATIONS

1. INDUCTOR :

By taking Z3 or Z5 as capacitive load and other impedances as

resistors, Yin becomes

=5

3124

=3124

5

Simulation result of impedance and phase variation with

frequency is shown in figure 3 and 4 respectively.

2. FREQUENCY DEPEDENT NEGATIVE RESISTOR :

By taking 1=1/1 ,5 = 5, 4=1/4 , 2=2, 3=3 becomes

= 21 4 3 5

2

Hence,

= 2

Fig 2:- CMOS implementation of CDBA.

Fig 2:- General Impedance Converter using three CDBA.

Figure 3:- Inductive Impedance variation with frequency

Where

=1 4 3 5

2

Circuit in Fig 5 is the FDNR circuit. Since the capacitance

generates a voltage proportional to the integral of the current,

the FDNR is an element that integrates the current twice. The

value of D is adjusted by varying one of the resistances

3.Band Pass filter Transfer function of band pass filter in fig is given by

=/

2 +

+ 1/

Where

=

=

1

Fig 4:- Phase variation of inductive load with frequency

The band pass filter designed is having center frequency of

503.33 kHz. Simulation result of passband is shown in fig 5.

Component values obtained are R=1k ohm, C=1 nf

=.1mH. = .1 is obtained by taking R1=R2=R3=1k, R4=3k and C5=300pf in fig. 6

Fig 5:-Inductor using GIC

Frequency

1.0KHz 10KHz 100KHz 1.0MHz

V(V1:+)/I(V1:+)

0

5K

10K

Frequency

1.0KHz 10KHz 100KHz 1.0MHz

P(-I(V1))

80d

90d

100d

Fig:- 6 Band pass filter with inductive load using GIC

Fig 7:- Frequency response of band pass filter

With = 503.33

Fig 8:- FDNR using GIC

IV CONCLUSION

A new GIC topology is implemented using three

CDBA.Inductor, FDNR and band pass filter is realized using

this topology to illustrate its application. Results from PSPICE.

simulation are in remarkable agreement with the expected ones.

Hence, in integrated circuit fabrication where inductors cause

trouble one can use GIC as an alternate option of inductor.

V ACKNOWLEDGEMENT

We owe particular thanks to our mentor Dr. Rajeshwari

Pandey for supporting and guiding us through out this work.

VI REFERENCES

[1] Cevdet Acar*, Serdar Ozoguz, A new versatile building block: current differencing buffered amplifier suitable for

analog signal-processing filters (CDBA) Microelectronics Journal 30 (1999) 157160

[2] Cem Cakir, Shahram Minaei, Oguzhan Cicekoglu Low voltage low power CMOS current differencing buffered

Amplifier Analog Integr Circ Sig Process (2010) 62:237244 DOI 10.1007/s10470-009-9350-

[3] Rajeshwari Pandey, Neeta Pandey, S.Paul, A.singh,

B.Sriram, K.Trivedi, New Topologies of lossless grounded inductor using OTRA Journal of Electrical and computer engineering, Volume 2011 Article ID 175130,6 pages, Hindawi

publication.

[4] 1D. Susan and 2S. Jayalalitha Frequency Dependent Negative Resistance-A Review Research Journal of Applied Sciences, Engineering and Technology page 2988-2994

Frequency

1.0KHz 10KHz 100KHz 1.0MHz 10MHz

V(CDBA_block:Z)

0V

100mV

200mV

[5] Ali mit Keskin,, Erhan Hancioglu CDBA-Based Synthetic Floating Inductance Circuits with Electronic Tuning

Properties ETRI Journal, Volume 27 page 239-242.