Radio frequency amplifier ppt
Most of the electronic systems require at least one stage of amplification. Hence amplifiers can be seen in almost all the electronic devices. Amplifiers are the devices that increase the amplitude of the input signal. The output of the power supply is modulated by the Amplifier. Amplifiers increase only the amplitude and the other parameters such as frequency and shape remain constant.
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Class C Amplifier – Working Principle, Applications, Advantages & Disadvantages
Choice of frequency: The Intermediate Frequency Amplifier IF of a receiving system is usually a compromise, since there are reasons why it should be neither low nor high, nor in a certain range between the two. Frequencies used: As a result of many years experience, the previous requirements have been translated into specific frequencies, whose use is fairly well standardized throughout the world but by no means compulsory.
These are as follows:. By and large, services covering a wide frequency range have IFs somewhat below the lowest receiving frequency, whereas other services, especially fixed-frequency microwave ones, may use Intermediate Frequency Amplifier as much as 40 times lower than the receiving frequency.
The IF amplifier is a fixed-frequency amplifier, with the very important function of rejecting adjacent unwanted frequencies. It should have a frequency response with steep skirts. When the desire for a flat-topped response is added, the resulting recipe is for a double-tuned or stagger-tuned amplifier. Whereas FET and integrated circuit IF amplifiers generally are and vacuum-tube ones always were double-tuned at the input and at the output, bipolar transistor amplifiers often are single-tuned.
A typical bipolar IF amplifier for a domestic receiver is shown in Figure It is seen to be a two-stage amplifier, with all IF transformers single tuned. This departure from a single-stage, double-tuned amplifier is for the sake of extra gain, and receiver sensitivity. Although a double-tuned circuit, such as those shown in Figures and , rejects adjacent frequencies far better than a single-tuned circuit, bipolar transistor amplifiers, on the whole, use single-tuned circuits for interstage coupling.
The reason is that greater gain is achieved in this way because of the need for tapping coils in tuned circuits. This tapping may be required to obtain maximum power transfer and a reduction of tuned circuit loading by the transistor. Since transistor impedances may be low, tapping is employed, together with somewhat lower inductances than would have been used with tube circuits. If a double-tuned transformer were used, both sides of it might have to be tapped, rather than just one side as with a single-tuned transformer.
Thus a reduction in gain would result. Note also that neutralization may have to be used capacitors C n in Figure in the transistor IF amplifier, depending on the frequency and the type of transistor employed. When double tuning is used, the coefficient of coupling varies from 0. Finally, the IF transformers are often all made identical so as to be interchangeable. Skip to content.
Low Power RF Low Noise Amplifier
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Introduction to the Amplifier
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ALL INDIA RADIO PPT
We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you! Published by Colleen Scott Modified over 6 years ago. F signal Detect modulated signal to get back original modulating signal Amplify modulating frequency signal.
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A radio frequency power amplifier RF power amplifier is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal. Design goals often include gain , power output, bandwidth, power efficiency, linearity low signal compression at rated output , input and output impedance matching, and heat dissipation. Some classes are class A , class AB, class B , class C , which are considered the linear amplifier classes. In these classes the active device is used as a controlled current source.
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 reduced conduction angle improves the efficiency to a great extend but causes a lot of distortion. Due to the huge amounts of distortion, the Class C configurations are not used in audio applications. The most common application of the Class C amplifier is the RF radio frequency circuits like RF oscillator, RF amplifier etc where there are additional tuned circuits for retrieving the original input signal from the pulsed output of the Class C amplifier and so the distortion caused by the amplifier has little effect on the final output. Input and output waveforms of a typical Class C power amplifier is shown in the figure below. From the above figure it is clear that more than half of the input signal is missing in the output and the output is in the form of some sort of a pulse.
A new dual-state impedance matching scheme for a microwave driven plasma lamp using a solid-state power amplifier SSPA is presented. The impedance of the plasma lamp depends on the amount of input radio frequency RF energy, and therefore has very different values for hot and cold states. First, a method for effectively modeling the electrical characteristics of a plasma lamp that depends on RF power has been proposed. Second, a new technique has been proposed to achieve dual-state impedance matching for two state impedances at two very close frequencies using a T-shaped matching network with two section shunt stub and additional transmission line. The proposed method can achieve dual state impedance matching in two frequency bands located very closely when compared to the conventional methods. The accuracy of the proposed model and the effectiveness of the proposed dual-state matching are verified via a plasma lamp system with a 2. Citation: Kang W, Ku H Modeling and impedance matching for radio frequency driven plasma lamp considering cold and hot states.
Choice of frequency: The Intermediate Frequency Amplifier IF of a receiving system is usually a compromise, since there are reasons why it should be neither low nor high, nor in a certain range between the two. Frequencies used: As a result of many years experience, the previous requirements have been translated into specific frequencies, whose use is fairly well standardized throughout the world but by no means compulsory. These are as follows:.
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