Exp no 3 setb118 Analog electronics
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This document describes an experiment to analyze the frequency response of an amplifier circuit. Key points: - The frequency response shows how the gain of a circuit varies with input signal frequency. An amplifier should maintain consistent gain across all audio frequencies to avoid distorting sound. - The experiment was conducted using a CE amplifier circuit in Multisim and hardware. Gain and bandwidth were measured with and without a bypass capacitor. - In both cases, gain decreased at high frequencies due to parasitic capacitances in the transistor. The bypass capacitor increased bandwidth by reducing gain, as expected theoretically. - 3dB is used to define bandwidth as it represents a 0.707 reduction in voltage gain, a common standard for measuring
Exp no 3 setb118 Analog electronics
- 1. Frequency Response of an Amplifier Experiment No 3 Batch B1 Bock 1 Omkar Rane SETB118 Rohit Mane SETB102 Abhishek Sainkar SETB104 Tanmay Kale SETB112 JULY 31, 2017 MIT ACADEMY OF ENGINEERING, DEPARTMENT OF ENTC ENGG. ANALOG ELECTRONICS LAB MANUAL
- 2. S.Y.B. Tech (ET): 2017-18 Analog Electronics EXPERIMENT No: 3 Frequency Response of an Amplifier Introduction: - A practical amplifier circuit increases the voltage level of the input signal. Signal obtained from radio or TV receiver circuit consists of a band of frequencies, e.g. from 20 Hz to 20 KHz. The amplifier must amplify all the frequency components of signal by same amount so that output of the loudspeaker will not be the exact replica of the original sound. If the loudspeakers are to reproduce the sound faithfully, then no distortion or attenuation has to be introduced by the amplifier Fig.1. a Fig. 1.b Objective: - To observe the frequency response of an amplifier To calculate Bandwidth of the circuit Pre-lab Questions: - Write significance of Frequency Response Ans) Frequency Response of an electric or electronics circuit allows us to see exactly how the output gain (known as the magnitude
- 3. S.Y.B. Tech (ET): 2017-18 Analog Electronics response) and the phase (known as the phase response) changes at a particular single frequency, or over a whole range of different frequencies from 0Hz, (d.c.) to many thousands of mega-hertz, (MHz) depending upon the design characteristics of the circuit. Generally, the frequency response analysis of a circuit or system is shown by plotting its gain, that is the size of its output signal to its input signal, Output/Input against a frequency scale over which the circuit or system is expected to operate. Then by knowing the circuits gain, (or loss) at each frequency point helps us to understand how well (or badly) the circuit can distinguish between signals of different frequencies. Lab Exercise: - 1. Draw the circuit diagram of Single stage CE amplifier here Post Lab. Question: - 2. Procedure: - (Write in your own words) Practical method:
- 4. S.Y.B. Tech (ET): 2017-18 Analog Electronics 1. Setup voltage divider bias CE amplifier on breadboard or multisim software. 2. Using signal generator set the input voltage for signal generator Vin. 3. Put coupling capacitor C1 in series with source. 4. +Vcc =12 V is provided by DC dual regulated power supply and ground the required connection as per circuit diagram. 5. C2 capacitor is bypass capacitor take reading of different voltages from CRO without and with bypass capacitor. Also note frequency values as per varying voltages. 6. Plot these values Voltage Vs frequencies on semi log paper. In this way, we can draw a frequency response curve. Software Method: 1. Using multisim software setup voltage divider single stage amplifier on workspace of multisim. 2. Drag marker tool to input and output of amplifier. set in input voltage of Vi=20V. 3. In simulate menu click on AC analysis option. 4. Set value to decibel and select voltage parameter. 5. Click on simulate option to get the frequency response graph. 3. List the Equipments / Component required for the experiment Equipment / Components Specifications/Values
- 5. S.Y.B. Tech (ET): 2017-18 Analog Electronics Function Generator CADDO,4061,3MHz Pulse Generator with 40 MHz Frequency Counter CRO HAL-TEC plus, HT4030,30MHz, Oscilloscope Resistor R1=8k, R2=2.7k,RC=3.3k, RE=1k Breadboard Variable Power Supply Radial Industry SVP030002D Transistor BC547{npn} National instruments Multisim software Ver 8 or 12 4. Observation Table (Multisim readings) Parameters With Bypass Capacitor Without Bypass Capacitor Gain 818mV/40mV = 20.45 129mV/40mV= 3.225 Bandwidth F2 = 19.0353MHz F1=12.4894KHz B=F2-F1 = 19.0353MHz F2 = 22.8292MHz F1=77.0535Hz B=F2-F1 = 22.8291MHz
- 6. S.Y.B. Tech (ET): 2017-18 Analog Electronics 5. Observation Table (Hardware readings) Vin = 20mV Frequency Voltage(Vout) Gain Gain in dB Low Frequency Region 50 Hz 4.76 V 238 47.531 100 Hz 8.13 V 406.5 52.181 500 Hz 10.21 V 510.5 54.159 Mid Frequency Region 1 KHz 10.22 V 511 54.169 50 KHz 10.22 V 511 54.169 200 KHz 10.22 V 511 54.169 1 MHz 10.22 V 511 54.169 High Frequency Region 10 MHz 9.25 V 462.5 53.302 50 MHz 4.06 V 203 46.149 100 MHz 2.27 V 113.5 41.019
- 7. S.Y.B. Tech (ET): 2017-18 Analog Electronics Frequency Response Curves: (With Capacitor and Without Curve) Frequency Response curve (With Capacitor) Frequency Response curve (Without Capacitor)
- 8. S.Y.B. Tech (ET): 2017-18 Analog Electronics Circuit diagram on multisim. Amplifier with Bypass Capacitor Amplifier without Bypass Capacitor Conclusion: - We have verified frequency response graph on multisim. Gain is inversely proportional to bandwidth. In the presence of bypass capacitor gain is reduced so bandwidth will increase. In case without bypass capacitor gain will decrease so bandwidth will increase in this case. We have observed this in frequency response graph.
- 9. S.Y.B. Tech (ET): 2017-18 Analog Electronics Post Lab. Questions: - 1. Why there is drop in gain at lower frequency and higher frequency Ans 1) At higher frequencies, the internal junction capacitors of transistor come into play, thus reducing the output and therefore the gain of amplifier. The capacitor reactance decreases with increase in frequency bypassing the majority of output. In some cases, the output gets fed back to input as negative feedback. 2. As the frequency of the input signal increases, the gain of the amplifier reduces. The factor responsible for the reduction in gain at higher frequencies is the presence of various capacitors as shown in fig. 2. They are not physically connected but inherently present with the device. Justify Fig. 2 Ans 2) These are parasitic capacitor present in transistor. At low frequencies, parasitic capacitance can usually be ignored, but in high frequency circuits it can be a major problem. In amplifier circuits with extended frequency response, parasitic
- 10. S.Y.B. Tech (ET): 2017-18 Analog Electronics capacitance between the output and the input can act as a feedback path, causing the circuit to oscillate at high frequency. 3. Why we take 3 dB down from the maximum gain to measure BW? Ans 3) The -3dB, come from 20 Log (0.707). Gain dB= 20 log(Av). Note :- Kindly attach screenshot of your performed experiments