Class C Amplifiers:
Class C amplifiers conduct less than 50% of input signal, permitting it to reach 90% efficiency but resulting in high distortion at output. Therefore, in Class C amplifier, output current (or voltage) is zero for more than 50% of input waveform cycle. In some appliances like megaphones, high distortion of Class C amplifiers can be tolerated. Likewise, Class C amplifiers can be utilized in tuned Radio Frequency applications as the distortion of class C amplifier can be considerably decreased by tuned loads.
In Radio Frequency and Tuned Load applications, input signal is utilized to roughly switch amplifying device on and off that causes pulses of current to flow through tuned circuit.
Class C amplifiers are like Class B in that output stage has zero idle bias current. Though, Class C amplifiers have the region of zero idle current that is more than 50% of total supply voltage. Drawbacks of Class B amplifiers are even clearer in Class C amplifiers, so Class C is similarly not practical for audio applications.
Class C applications are mainly radio frequency applications where highly distorted output of amplifier can be filtered out by tuned circuit.
Applications like FM transmission where linearity is not significant often apply class C power output amplifiers stages.
Modes of class c amplifier:
Class C amplifiers have two modes of operation which are tuned mode and the untuned mode of operation. In untuned operation, waveform analysis will demonstrate massive distortion in signal and when proper load like pure inductive-capacitive filter is utilized, two things will take place. First is that output's bias level is clamped, so that output variation is centered at one-half of supply voltage. This is why tuned operation is at times known as clamper operation. This action of inspiring bias level permits waveform to be restored to proper shape, permitting complete waveform to be re-established despite having only one-polarity supply. The second thing to take place is that waveform on centre frequency becomes much less distorted and distortion which is present is dependent on bandwidth of tuned load, with centre frequency experiencing very little distortion, but experiencing greater attenuation the farther from tuned frequency that the signal gets.
The tuned circuit will only resonate at specific frequencies, and so unwanted frequencies are noticeably suppressed, and wanted full signal (sine wave) will be extracted by tuned load provided the transmitter is not needed to operate over very extensive band of frequencies. Tuned mode Class C amplifier works very well and other residual harmonics can be removed using filter.
Output characteristics of Class C power amplifier:
In the above figure operating point is placed some way below cut-off point in DC load-line and so only fraction of input waveform is available at output.
Class C power amplifier circuit:
Biasing resistor Rb pulls base of Q1 further downwards and Q-point will be set some way below cut-off point in DC load line. Thus transistor will start conducting only after input signal amplitude has risen above base emitter voltage (Vbe~0.7V) plus downward bias voltage caused by Rb. That is the reason why major portion of input signal is absent in output signal.
Inductor L1 and capacitor C1 forms the tank circuit that helps in extraction of required signal from pulsed output of transistor. Actual job of active element (transistor) here is to generate the series of current pulses according to input and make it flow through resonant circuit. Values of L1 and C1 are so selected that resonant circuit oscillates in frequency of input signal. As resonant circuit oscillates in one frequency (usually carrier frequency) all other frequencies are attenuated and needed frequency can be squeezed out using the properly tuned load. Harmonics or noise present in output signal can be eliminated utilizing extra filters. The coupling transformer can be utilized for transferring power to load.
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online physics tutoring. Chat with us or submit request at [email protected]
animal kingdom tutorial all along with the key concepts of characteristics of invertebrates, difference invertebrates and vertebrates, phylum protozoa, features of phylum protozoa, categorization of protozoan and amoeba phylum
It might not be out of place here to understand the mean of the word ‘value’. Since a matter of fact, the word ‘value’ comprises dissimilar meanings for dissimilar persons.
tutorsglobe.com electronegativity scales assignment help-homework help by online chemical periodicity tutors
a counter is a device that stores (and occasionally displays) the number of times a specific event or process has happened, frequently in relationship to a clock signal.
tutorsglobe.com explanation of the law assignment help-homework help by online equi-marginal utility tutors
Electron Dynamics tutorial all along with the key concepts of Definition of electron dynamics, Effective mass and Current density
tutorsglobe.com advantages-disadvantages of self-pollination assignment help-homework help by online self pollination tutors
tutorsglobe.com peripheral lymphoid organs assignment help-homework help by online structure and functions of immune system tutors
metals-transition metals tutorial all along with the key concepts of electronic configuration of 1st transition series metals, physical properties of transition metals, chemical reactivity, variable oxidation states, complex ion formation, alloy
Pharmaceuticals tutorial all along with the key concepts of Antibiotics, Production of Penicillin, Production of Acetylsalicylic acid or aspirin and Production of Tetracycline
Reserves are profits and gains that a company has made and that still form part of the equity of shareholders.
tutorsglobe.com economics, mathematics and statistics assignment help-homework help by online positive or normative economics tutors
tutorsglobe.com binding energy of nucleus assignment help-homework help by online nuclear reaction tutors
Lower Invertebrates tutorial all along with the key concepts of traits of Invertebrates, Categories of invertebrates, Arthropods, Sponges, Cnidarians, Segmented worms, Flatworms, Roundworms, Mollusks and Echinoderms
www.tutorsglobe.com offers requirement elicitation homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
1949406
Questions Asked
3689
Tutors
1470913
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!