A Simple Current Mode Schmitt Trigger Circuit Based On Single CCDDCCTA without Employing Any Passive Components

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Volume 3, Issue 8, 2016

17 Available online at www.ijiere.com

International Journal of Innovative and Emerging

Research in Engineering

e-ISSN: 2394-3343 p-ISSN: 2394-5494

A Simple Current Mode Schmitt Trigger Circuit Based On

Single CCDDCCTA without Employing Any

Passive Components

Rupam Das

a

_{, Khushi Banerjee}

b

a,b_{Assistant Professor, ECE Department, Asansol Engineering College, WB, India}

ABSTRACT:

This paper introduce a new current mode Schmitt trigger circuit using a single Current Controlled Differential Difference Current Conveyor Transconductance Amplifier (CCDDCCTA). The circuit is designed using a single CCDDCCTA without any passive component. The proposed Schmitt trigger circuit is designed at a supply voltage of ±1.25V, bias voltage of -0.8V using PSPICE and the model parameter of 0.25µm CMOS TSMC technology is used for simulation. The circuit presented in this paper is insensitive to temperature operates at a low frequency, low voltage.

Keywords: CCDDCCTA, Schmitt Trigger, Current mode, Low voltage.

I. INTRODUCTION

Both in Analog and Digital domain Schmitt trigger circuits are used. It poses a property of converting a varying voltage into a stable logical signal. Schmitt trigger circuit has many applications such as Square waveform generator [1-3], Pulse width modulator [4-6], Mono stable multivibrator [7-8], Function generator [9], etc.

Due to wide bandwidth and large dynamic range as compare to operational amplifier based circuit recently various new current mode building block has find considerable attention. The building block which support this current mode versions are current conveyor (CC) [10], Differential Voltage Current Conveyor (DVCC) [11], Differential Difference Current Conveyor (DDCC) [12], Multiple Output Current Controlled Conveyor Differential Transconductance Amplifier (MO-CCCDTA) [13] etc. Recently a new current mode building block is introduced CCDDCCCTA [14]. It is basically a combination of Current controlled differential difference current conveyor (CCDDCC) [15] followed by transconductance amplifier block. It has high output impedance terminal for current and high input impedance terminal for voltage. CCDDCCTA building block has all the good properties of CCDDCC and DDCCTA [16] along with electronic tuning of transconductance with lesser no of resisters and integrated circuit implementation.

In 1938, O.H.Schmitt first introduces the Schmitt trigger circuit as thermionic trigger [17]. Using OPAMP Schmitt trigger is designed with one active block and three passive components [18]. Schmitt trigger circuits based on current conveyor using 2 active building block and 4 passive components. [19]. Current conveyor (CC) based Schmitt trigger circuit [20] has large number of passive components and in [21] the circuit is also designed using OTA uses maximum number of active and passive components. Operational transresistance amplifier (OTRA) based Schmitt trigger circuit [22] uses a switch and a floating resistor. The Schmitt trigger circuit designed by DVCC [23] uses a single active building block and two passive components In [24] the Schmitt trigger circuit is also been proposed by the building block CDTA. In [25] the Schmitt trigger circuit is designed by CMOS based MO-CCCDTA at 65nm technology with a supply voltage of ±0.75v. In [26] Schmitt trigger circuit is designed by MO-CTTA without any passive components.

The presented paper is organised as follows Section II deals the basic concept of CCDDCCTA building block. Section III represents the proposed circuits and its operation, Section IV refers the simulation results and conclusion is given in Section V.

II. CCDDCCTA FUNDAMENTALS

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Fig.1: Symbol of CCDDCCTA

Fig.2: Implementation of CCDDCCTA using CMOS

The port relationships of the CCDDCCTA can be represented by the following matrix:

Where the intrinsic resistance (Rx) at X terminal defined as

X

m16 18

1 R =

g

+g

Where ,

m16 ox 16 B1

W

g

= 2μC (

) I

L

m18 ox 18 B1

W

g

= 2μC (

) I

L

Similarly the transconductance (gm0)from z terminal to O terminal may be expressed as:

mo ox 25,26 B2

W

g

= 2μC (

)

I

L

III. PROPOSED CIRCUIT

The proposed Schmitt trigger circuit is designed by using a single CCDDCCTA analog building block is shown in Fig.3 and its transfer characteristics is shown in Fig.4.Here input is applied to terminal X ,Y1 terminal is grounded and the Y2,Y3

terminal are connected in the feedback to terminal Z. We take the output from Z. Here input is applied to terminal X and the current at X port is raised from IX to +IX .the output current is +IO to –IO .similarly the current at X port is raised from

+IX to–IX .The output current is –IO to+ IO

The output current can be controlled by IB2 so the proposed Schmitt trigger can be written as

IO ={-IB2 for Ii > 0

IB2 for Ii < 0 }

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IV.SIMULATION RESULTS

The proposed circuit is simulated using PSPICE and 0.25µm CMOS TSMC technology process parameter. The W/L ratio of CMOS transistor in CCDDCCTA analog building block is given in Table.1. in this proposed circuit there are 2 points where we can take the output. First from O+ and another is O- .When we take the output from O+ then we observe the CW waveform and when we are taking the waveform from O- then we observe the CCW waveform. First we observe the output from O+ terminal for that a sinusoidal input waveform with a frequency 10 KHz with current amplitude of ±150µA is applied to the Schmitt trigger circuit. The input and the corresponding output of the applied waveform is shown in Fig.4. A triangular input wave form of ±150uA amplitude and 10 KHz waveform is also applied to the circuit and the corresponding input output waveform is also shown in Fig.5. The hysteresis curve is also shown in Fig.6. Similarly for the CCW waveform we observe the input and output wave form for the sine wave and the triangular wave in Fig.7 and Fig.8. The hysteresis wave for this case is shown in Fig .9 respectively. The supply voltage ±1.25V and VBB=-0.8V is used in this circuit . The proposed Schmitt trigger circuit is suitable for low power and low voltage

application .Here transfer characteristics curve are depend on bias current IB. Comparison of previously published papers

with the proposed work is given in Table.2. Table.1: W/L ratio of various transistors:

Transistors Aspect ratio

W(µm)/L(µm)

M1,M4,M9,M11-M15,M30-M31, M38-M39 3/.25

M2,M3,M5,M6 1/.25

M7-M8,M20-M23,M26,M28-M29,M32-M33,M34 5/.25

M10 12.5/.25

M16-M17 8/.25

M18-M19 5/.25

M24-M25,M36-M37 5/.25

M27,M35 4.35/.25

Fig.4:Input and output wave form of the proposed circuit.

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Fig.9: Hysteresis curve of the proposed circuit.

Table.2: Comparison with the previously published papers:

Ref no ABB Technology

Used

BJT/MOS Based Design

No of Active

Block

No of Passive Components

CW+CCW BOTH

Supply Voltage

18 OPAMP - IC 1 3 NA ±12V

19 CCII AD844 IC 2 4 NA ±6V

20 CCII QN/QP-2222 BJT 1 3 NA ±5V

21 OTA LM13600 BJT 2 2 NA ±10V

22 OTRA AD844/AN MOS 1 1 YES ±10V

23 DVCC .25µm MOS 1 2 NA ±1.25V

24 CDTA .25µm MIETEC MOS 1 2 NA -

25 CCCDTA .65nm MOS 1 0 NA ±1.5V

26 MO-CTTA AD844 IC 1 0 NA ±5V

Proposed CKT

CCDDCCTA .25µm TSMC MOS 1 0 YES ±1.25V

V. CONCLUSION

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