Secondly, we would need to set the value for frequency and amplitude. When the collector current flows for less than half cycle of the input signal, the power amplifier is known as class c power amplifier. Less than one half cycle means the conduction angle is less than 180 and its typical value is 80 to 120. This handout gives an introduction to these amplifiers and a smattering of the various configurations that they can be used in. Circuits laboratory experiment 9 operational amplifiers. Thus the class c amplifier model is implemented using theactivate tool. Class c bjt amplifiers worksheet discrete semiconductor. In class c power amplifier, the base is negatively biased, so that collector current does not flow just when the positive halfcycle of the signal starts. Students are liable to wonder why class c operation is not the most popular in electronic circuits, since it is the most power efficient of the three classes.
For the voltagedivider dc bias configuration see fig. Eee 331 analog electronics lab experiment 6 power amplifiers a. Generally, in class c amplifier, load is a tuned circuit, which selects the fundamental or the desired harmonic rejecting all. The output amplifier circuit consists of two transistors bc 548b. Classb push pull amplifier switch on the power supply and signal generator.
Class b push pull amplifier switch on the power supply and signal. An amplifier receives a signal from some pickup transducer or other input source. These classes are not only used in power amplifier but also used in audio amplifiers circuits. Objective the purpose of these experiments is to introduce the most important of all analog building blocks, the operational amplifier op amp for short. While shorting 2 or more wires for common connections like grounding, do not twist wires. The classes theoretical efficiency, linearity, biasing, and applications are briefly covered. Observation book of the present lab experiment should be get corrected on the same day and record should be corrected on the next scheduled lab session. This paper explores some unique techniques and models for simulating amplifiers running in class c operation using the general purpose spice circuit simulation program. The purpose of the experiment is to analyze and plot the frequency response of a common collector amplifier. A practical class s power amplifier for high frequency. Only the circuits creator can access stored revision history.
The class c power amplifier is one kind of amplifier where the transistor conduct for less than 180 onehalf cycle of the input signal and its typical value is 80 to 120. The efficiency of a power amplifier may be increased using the following fig. In this operation, class c amplifier also gives huge distortion across the output. A photograph is shown in figure 3, with a layout in figure 4.
Benha university faculty of engineering at shoubra l. In a singleended design, more gain is dangerous, due to parasitic feedback paths which limit stability. Its efficiency is about 75% because the active device is biased beyond cutoff. It is commonly used in rf circuits where a resonant circuit must be placed at the output in order to keep the sine wave going during the nonconducting portion of the input. Background class a stage the amplifier given in fig. Patil,iitbombay 3 resistance ro ideally zero, and gain av 0. A class ab amplifier has less fidelity, and class b and class c amplifiers have low or poor fidelity. The cmoy headphone amp is a popular headphone amplifier that is small enough to carry everyday. Keywords remote lab, bjt, class ab amplifier, experiments.
Ee 43100 operational amplifiers 1 opamps experiment theory 1. After completing this experiment, you should be able to, 1 observe the class c power amplifier s output waveform with resistive load. Our goal in this experiment is to measure av 0, ri, and ro of the ce ampli. Results of the simulation of an 870meghz amplifier including the transient, power gain, power dissipa. Eee2204 electronic circuits ii lab ahsanullah university.
For the power delivered to the circuit, the power spent over the base circuitry is neglected and the. Experiment the experiments will be performed with a. One fun and cool thing for ardent audio folks to do is switch the volume of an audio. Primary objective of this case study is to experiment on class c tuned power amplifier. A computerized study of the classcbiased rfpower amplifier. The reduced conduction angle progresses the efficiency to a great expand, but roots a lot of distortion.
A common class of operation used in radiofrequency rf amplifier circuits is class c. Output signal is only taken from the positive peak points of input signal. Experiment 6 transistors as amplifiers and switches. The output signal waveform is high distorted and rich in harmonic. Audio amplifier circuit university of california, santa barbara. It is mandatory to come with observation book and lab record in which previous experiment should be written in record and the present labs experiment in observation book. Ombura project report submitted in partial fulfillment of the requirement for the award for the degree of bachelor of science in electrical and electronics engineering of the university of nairobi 2016. Class c power amplifier circuit diagram and theory. Class b power amplifier circuit provides an output signal varying over one half the input cycle. This article discusses the working of the common emitter amplifier circuit and its applications. The classes are based on the proportion of each input cycle conduction angle during which an amplifying device passes current.
This circuit will look very strange if you are accustomed to analyzing audio. Class a power amplifier circuit theory design circuit. Class ab and class c power amplifiers tutorialspoint. Pushpull class b and class ab amplifiers analog devices. The efficiency of an amplifier refers to the ratio of outputsignal power compared to the total input power. Primary objective of this case study is to experiment on classc tuned power amplifier. Class a design produces good linear amplifiers, but are wasteful of power. Frequency response of common collector amplifier objective the purpose of the experiment is to analyze and plot the frequency response of a common collector amplifier. Tuned amplifier provide high constant gain over a specified bandwidth centered at a specified frequency f and 8s much rejection as possible outside this band practical gain and phase characteristics are shown in fig. The audio amplifier will be a selfcontained, batteryoperated component. Design and test class c tuned amplifier at centre frequency. Class c power amplifier lab manual this project will introduce two common power amplifier topologies, and also this lab introduces two amplifier topologies.
The lab workbenches overview each power lab bench is designed as a complete test station, with its own safety features and protective mechanisms. Generally, in class c amplifier, load is a tuned circuit, which selects the fundamental or the desired harmonic rejecting all other frequency components. In this lab we will first build a pushpull class b commonemitter amplifier comprised of one npn and one pnp transistor and use this to illustrate the large. The usage of reactive components like l and c, minimizes the power loss, which makes the tuned amplifiers efficient. In class c operation, somewhat less than half of the input signal appears amplified at the output. Power amplifier circuits output stages are classified as a, b, ab and c for analog designsand class d and e for switching designs. Background of class a amplifier class a amplifier report measured readings and implementation process firstly, we need to on the power button for the function generator and the digital storage oscilloscopedso. The data below were collected for the example of a npn 2n36443 transistor using the circuit. Objective the purpose of these experiments is to introduce the most important of all analog building blocks, the operational amplifier opamp for short.
The selectivity and amplification of desired frequency is. If you want to experiment using this amplifier as a linear, you can try setting the bias trimmer potentiometer to achieve a higher idle current during transmit, of. Ece 2c laboratory manual 2 mos amplifier basics overview. Class ab and class c power amplifiers the class a and class b amplifier so far discussed has got few limitations. The commonemitter class ab stage is used in railtorail operational amplifier op amp stages in order to allow the output voltage to swing very close to the power supply voltages. The battery was 9 volts and is the power supply in the lab. Class a power amplifier is the simplest of all power amplifier configurations. Class a amplifier circuit operation and applications. Ete 331 analog electronics lab experiment 8 power amplifiers a. Let us now try to combine these two to get a new circuit which would have all the ad.
Class ab amplifier part 2 in part 1 you built a simple class b amplifier. If the input is a sinusoidal, then the output is also sinusoidal over the dc biasing voltage fig. A class b power amplifier circuit provides an output. The class ab pushpull output circuit is slightly less efficient than class b because it uses a small quiescent current flowing, to bias the transistors just above cut off as shown in fig. The transistor characteristics are useful in amplifier design as well as understanding how transistors operate. The conduction angle for class c is less than 180 o. During this operation, the signal gets its proper shape and the center frequency became less distorted. The class c amplifier is used in the applications like rf oscillators, rf amplifier, fm transmitters, booster amplifiers, high frequency repeaters and tuned amplifiers. Power su ppl y 2231a303 power su ppl y from keith ley or any. The class a amplifier is the simplest form of power amplifier that uses a single switching transistor in the standard common emitter circuit configuration as seen previously to produce an inverted output.
The fixed resistor is 1 kw while the variable resistor is actually several. In conclusion, a class a amplifier has a high degree of fidelity. The most commonly used type of power amplifier configuration is the class a amplifier. Since the transistors in class a amplifier, are forward biased all the time, few current will flow through them even though there is no input signal and this is the main reason for its poor efficiency. This signal is generally small and needs to be amplified sufficiently to operate an output device. Common emitter configuration commonly used in lownoise amplifiers. Background of class a amplifier class a ampli fier report measured readings and implementation process firstly, we need to on the power button for the function generator and the digital storage oscilloscopedso. The main criterion for a power amplifier is not the power gain but the maximum a. Objectives study and characterize bjt amplifier in common emitter ce configuration. Before coming to the lab read through the lab experiment to familiarize yourself with the components and assembly sequence. The following are the advantages of tuned amplifiers. At first, the input voltage level is improved using voltage amplifier and this is then fed to power amplifier to obtain sufficient power. Explain what this means, contrasting it against the class a and class b operations common in audiofrequency amplifier circuits. However, the output of the pa is usually unmatched in order to maximize ef.
The purpose of class a bias is to make the amplifier relatively free from distortion by keeping the signal waveform out of the region between 0v and about 0. This operating class is a form of amplifier operation using pulse digital signals, which are on for a short interval and off for a longer interval. The benches have space for instrument operation and for storage, rotating machines, and power connections. This is due to the fact that the signal voltage must rise above a certain threshold before the transistors will even turn on. Radhakrishna rao, department of electrical engineering,iit madras. Class a amplifier design introduction to amplifier design basic design process. Turn the power switch on back of the work station 3. If the collector current flows for less than halfcycle of the input signal, it is called class c power amplifier. Power supply vcc and resistors r1 r4 should set bjt to operate in the forwardactive mode with required small. The amplifier is said to be class a power amplifier if the q point and the input. In the second part of the lab you will construct a. Circuits laboratory experiment 9 operational amplifiers 9.
Equipment and components used 30 mhz dual channel cathode ray oscilloscope 3 mhz function generator 030 v dc dual regulated power supply 4. Commonemitter amplifiers are also used in radio frequency transceiver circuits. When the circuit is exposed to a tuned load, the circuit clamps the output bias level with the average output voltage equal to the supply voltage. This is called untuned operation, and the analysis of the waveforms shows the massive distortion that appears in the signal. Know all about classc power amplifier circuit and tutorial. I play a little fast and lose with some of the math. Browse through a total of 48 audio amplifier circuits and projects. A manual for undergrad students teaching staff article pdf available august 2015 with 16,764 reads how we measure reads. This module shows how to simply calculate the values needed to make a working amplifier that has correct class a bias as described in amplifier.
Class a power amplifier is a type of power amplifier where the output transistor is on full time and the output current flows for the entire cycle of the input wave form. Although simple and more power efficient than the rest of the amplifiers in this lab, class b amplifiers suffer from severe crossover distortion. Power amplifiers purpose of a power amplifier generate high output power efficient conversion of dc power to rf power linear amplification generally pas will be common source cascode inductor is a choke to provide d apacitor is a ac coupling path to output james buckwalter 2. Below, we will demonstrate traditional power amplifier classes ranging from class a, b, ab and c, and also demonstrate class d amplifier which is widely used in switching designs. A nonlinear circuit will distort the input waveform.
Additional experiment mos amplifier 52 design experiment shunt voltage regulatorsoftware experiment 57. Class c amplifier class c amplifier operates for less than half of the input cycle. Class a is least efficient, followed by class b, and then class c which is most power efficient. Experimental rfpower amplifier and measurement setup. The main advantage of the class c amplifier is, it has a lowest physical size for a given power output. Not ssb as it is it is designed as a class c amplifier, for cw operation or fsk modes. A practical class s power amplifier for high frequency transmitters. Hence, the effectiveness of a power amplifier is measured in terms of its ability to convert d. The class a power amplifier we build in this lab will include two stages, first stage using common emitter ce amplifier and second stage using common collector cc amplifier. The efficiency of class c amplifier is high while linearity is poor.
Tpa3122d2 ic is used as a class d audio amplifier and can deliver up to 15w of power. Acquire hands on laboratory experience, utilizing oscilloscopes and other test. Pdf remote laboratory exercise for class bab power amplifier. Power amplifier classes the power efficiency of an amplifier, defined as the ratio of power output to power input, improves gets higher going from class a to class d.
Here focus on an amplifier that has tuned collector load and active device transistor operating at class c mode and observe the output voltage and current relationship at different harmonics. Sep 05, 2008 lecture series on electronics for analog signal processing partii by prof. Before coming to the lab, each group should obtain a parts kit from the ece shop. Common emitter amplifier working principle and its.
To plot frequency response of class c power amplifier. Class c power amplifier is a type of amplifier where the active element transistor conduct for less than one half cycle of the input signal. The diagram shows a waveform from a simple classc circuit without the tuned load. The output impedance, z o, is that seen looking from the load into the output of the amplifier. Introductory electronics laboratory 6i experiment 6 transistors as amplifiers and switches our final topic of the term is an introduction to the transistor as a discrete circuit element.
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