International Journal of Electronics and Communication Engineering & Technology (IJECET) Volume 6, Issue 8, Aug 2015, pp. 28-34, Article ID: IJECET_06_08_005 Available online at http://www.iaeme.com/ijecetissues.asp?jtypeijecet&vtype=6&itype=8 ISSN Print: 0976-6464 and ISSN Online: 0976-6472 IAEME Publication BAND PASS DESIGN WITH FLOATING RESISTOR SIMULATION APPLICATION AS FEEDBACK USING OPERATIONAL TRANSCONDUCTANCE AMPLIFIER Manjula V. Katageri Government First Grade College, BAGALKOT, India M. M. Mutsaddi Basaveshwar Science College, BAGALKOT, India Rajeshwari S. Mathad Basaveshwar Science College, BAGALKOT, India ABSTRACT The simulation of resistance using OTA has shown stable results of resistance which have close agreement in theoretical and in practical values using simulation circuits. A simulation of floating resistor of different values has been used as feedback in OTA band pass structure. A close observation of the structure in band pass range has good agreement in theoretical values and practical values of the circuit. A band pass is observed in tunable range of frequency from the bias current with a designed quality factor. The designed filter has applications in instrumentation using transducers. Key words: Resistance simulation, OTA-Operational Transconductance Amplifier, Band pass filter Cite this Article: Manjula V. Katageri, M. M. Mutsaddi and Rajeshwari S. Mathad. Band Pass Design with Floating Resistor Simulation Application as Feedback Using Operational Transconductance Amplifier. International Journal of Electronics and Communication Engineering & Technology, 6(8), 2015, pp. 28-34. http://www.iaeme.com/ijecet/issues.asp?jtypeijecet&vtype=6&itype=8 1. INTRODUCTION Electronically tunable resistors have significant role in the analog circuit design. They are useful in variety of applications in analog circuit in voltage controlled amplifiers, automatic gain controlled circuits, automatic tuned filters and oscillators. The Operational Transconductance Amplifier is one device, in which the transconductance http://www.iaeme.com/ijecet/index.asp 28 editor@iaeme.com
Band Pass Design with Floating Resistor Simulation Application as Feedback Using Operational Transconductance Amplifier property helps to simulate grounded and floating resistors with respect to bias current. The simulated resistances from ohms to hundreds of K ohms are obtained with respect to single parameter of variation of biasing current of OTA. Using the floating simulated resistor the band pass filter with minimum number of OTA is designed. The Operational Transconductance Amplifier is a device in which the input voltage controls the output current. It contains the feature of linear controlled transconductance with tunable property of bias current. The magnitude of resistance can be electronically varied by changing the external bias current of OTA. LM13600/LM13700 consists of two current controlled transconductance amplifiers with different inputs and push pull outputs. The ideal OTA has Z in =, Z out =, Inverting input current is equal to non inverting input current. The Fig.1 shows circuit symbol of OTA. The voltage controlled current source is mathematically expressed as, I out = g m (V A - V B ), Where g m = (I bias /2V T ), V T is thermal Voltage = T/11600 =26mV at 28 0 C of room temperature. Fig.1 Circuit symbol of OTA 2. CIRCUIT DESCRIPTION The simulation of the grounded resistor by taking feedback path of OTA on either of the input terminal for positive and negative resistor respectively as shown in Fig (2). The resistance values are varied with respect to biasing current is given by the Eqn. (1) R = = (1) Figure 2 Simulated grounded Resistor The floating resistor can be simulated with two OTAs as shown in Fig.3. By analysis of the circuit, it gives an admittance matrix as Y = where R = 1/g m (2) Thus realizes the ideal floating resistor. http://www.iaeme.com/ijecet/index.asp 29 editor@iaeme.com
Manjula V. Katageri, M. M. Mutsaddi and Rajeshwari S. Mathad Figure 3 Simulated floating resistor The simulated floating resistance is verified through band pass structure using one OTA with feedback floating resistor, which is shown in Fig. 4. The resistance is replaced with the simulated floating resistor of two OTA circuit as shown in Fig. 5. Figure 4 Band pass filter with feedback resistor Figure 5 Bandpass filter with simulated feedback resistor http://www.iaeme.com/ijecet/index.asp 30 editor@iaeme.com
Biasing Current in μa Band Pass Design with Floating Resistor Simulation Application as Feedback Using Operational Transconductance Amplifier By analyzing the circuit the transfer function of Band pass filter at g m1 =g m2 =g m is obtained as The centre frequency is and quality factor is This is verified experimentally through Proteus Professional Software. 3. EXPERIMENTAL RESULTS The simulated grounded and floating resistor values are experimentally verified with LM13600 of OTA [3-6]. The bias current of OTA is varied from 0.1uA to 1mA at room temperature, which gives theoretical values of resistances in the range 520KΩ to 0.052KΩ respectively. These are verified using Proteus Professional Software which produces good results in filter designs. In the laboratory, the simulated values are in well agreement with theoretical values for biasing current in between 10uA to 500uA. Beyond this range there is variation in simulation of resistance, because the input offset voltage varies as biasing current near 1uA and 1000uA of LM13600N OTA. The variation of bias current with log R is shown in Fig.6 [1-6]. 10000 Variation of biasing current Vs. Log R 1000 100 10 R(Th) R(Pr) 1 0.1 0.01 0 1 2 3 4 5 6 7 Log R Figure 6 Variation of biasing current with Log R The same simulated resistances are used in the design of band pass filter, shown in Fig. 7. For unity quality factor I B1 =I B2 =I B3 =I B, & C 1 =C 2 =C. At I bias = 100µA & C = 10nF, the centre frequency f o = = 30.5KHz theoretically, where as experimental observation gives well structure of band pass filter of f o = 30.9 KHz with -3.0db gain and bandwidth of 57.2KHz with roll off rate -40db per decade is shown in Fig.8. http://www.iaeme.com/ijecet/index.asp 31 editor@iaeme.com
6 7 8 11 1 2 1 2 6 10 9 7 8 11 6 11 16 15 Manjula V. Katageri, M. M. Mutsaddi and Rajeshwari S. Mathad U1:B(AMPBIAS) U2:A(V-) U1:B(V+) U2:A U1:B 5 4 3 14 13 12 LM13600 LM13600 input Vin C1 Vout 10nf U1:A U1:A(AMPBIAS) 3 4 5 C2 10pf LM13600 Figure 7 Experimental simulated Band pass filter This simulated resistance is verified in band pass for biasing currents from 1µA to 1000µA, which gives a very good agreement with theory. At I B1 =I B2 =I Bias = 100µA for simulated resistance of 520Ω, C 1 = 10nF and C 2 = 10pF, for I B3 = 1uA gives a wide band pass filter with -20dB per decade roll off. The -3dB frequencies are ranging from. 204 Hz to 9.75 MHz & its band width is 9.749MHz, which is shown in Fig. 9. The flatness of band pass filter depends on the difference between values of capacitors. Greater the difference greater will be the flatness and the positive gain changes with respect to the capacitor C 2 and the bandwidth depends on biasing currents. This is advantageous parameter which helps to select the bandwidth with positive gain. [7-10] Figure 8 Frequency Response at Q=1 http://www.iaeme.com/ijecet/index.asp 32 editor@iaeme.com
Band Pass Design with Floating Resistor Simulation Application as Feedback Using Operational Transconductance Amplifier Figure 9 Frequency Response for wide band structure 4. CONCLUSION The simulation of grounded and floating resistance using Operational Transconductance Amplifier gives a well agreement with theoretical values. The application of simulated floating resistance in feedback of OTA band pass filter shows good results in respect of the selectivity. For unity quality factor the biasing currents and capacitors of desired equal value gives narrow band pass filter, whose centre frequency can be selected with reduced bandwidth [3-10]. A basing current of 1μA with floating resistor of 520Ω gives wideband pass structure with C 1 greater than C 2 gives bandwidth 9.7MHz. This bandwidth with positive gain is dependent on the difference between C 1 and C 2. Greater the difference greater will be the flatness is observed. For selected values of C1 and C 2 with C 1 greater than C 2 the bandwidth is more selective to the biasing currents of I B3 with respect to simulate floating resistance. The floating resistor simulation is one advantageous for selecting the bandwidth, centre frequency and quality factor with respect to biasing current of Operational Transconductance Amplifier. The designed filter has applications in instrumentation using transducers. REFERENCES [1] Randll L. Geiger and Edgar Sanchez- Sinencio Active Filter Design Using Operational Transconductance Amplifiers: A Tutorial, IEEE Circuits and devices Magazine, 1, March 1985, pp 20-32 [2] I.A. Khan, M. T. Ahmed. Realisation Of Tunable Floating Resistors, Electronics 22(5), Letters 17 th july 1986 [3] Khanittaha Kaewdang, kiattisak Kumwachara and wanlop Surakampontorn, Electronicallytunable Floating Cmos Resistor Using Ota, IEEE, Proceedings of ISCIT 2005 [4] R.G.Carvajal, J Galan, A, Torralba and et. Al. A Very Linear Ota With V-I Conversion Based On Quasi-Floating MOS Resistor, IEEE, 1-1244-0921-7/07, 2007 http://www.iaeme.com/ijecet/index.asp 33 editor@iaeme.com
Manjula V. Katageri, M. M. Mutsaddi and Rajeshwari S. Mathad [5] Bhaba priyo Das, Neville Watson and yonghe Liu, Simulation of Voltage Controlld Tunable All Pass Filter Using 1700 Ota, International Journal of Electrical and Computer Engineering 5-6-2010 [6] Montree Kumngern. New Electronically Tunable Voltage Mode Low Pass,High Pass, Bandpass Filter Using Simple Ota s, International Journal And Electrical Engineering, 3(5), 2011, pp-649-53 [7] Dattaguru V. Kamath. Novel of OTA-C current mode third order band pass filters, International journal of innovative research in electronics, instrumentation and control engineering,2(8), August 2014 [8] Rajeswari S. Mathad and et. al, Studies on active filters using OTAC and oyher current conveyors, International Journal of advanced Computer and mathematical Sciences, 2(3), 2011, pp 155-159 [9] Montree Kumngern. New electronically tunable voltage mode low pass,high pass, band pass filter using simple OTA s, International Journal of Computer and Electrical engineering, 3(5),Oct-2011 [10] Jagadeep Kaur sahani, et.al, Design of second order low pass and high pass filter using double gate Mosfet based OTA, Innovative systems design and engineering 5(4),2014 [11] Roma Rani, Pankaj Rai and Jyoti Athiya. Design and Analysis of Second Generation Current Conveyor Based Low Power Operational Transconductance Amplifier. International Journal of Electrical Engineering & Technology, 6(4), 2015, pp. 9-15. [12] Mohammed Arifuddin Sohel, Dr. K. Chennakeshava Reddy and Dr. Syed Abdul Sattar. Linearity Enhancement of Operational Transconductance Amplifier Using Source Degeneration. International Journal of Advance in Research Engineering & Technology, 4(2), 2015, pp. 257-263. http://www.iaeme.com/ijecet/index.asp 34 editor@iaeme.com