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Low Noise Amplifier Question & Answers

July 8, 2022 By WatElectronics

This article lists  50 Low Noise Amplifier (LNA) MCQs for engineering students. All the Low Noise Amplifier (LNA)  Questions & Answers below include a hint and a link to the relevant topic wherever possible. This is helpful for users preparing for their exams, interviews, or professionals who would like to brush up on the fundamentals of Low Noise Amplifier (LNA).

Amplifiers in the communication system enhance the signal's strength and increase the power of noise & signal present in the input. Because of the passive and the active components present the overall noise present in the circuit increases.

To overcome such noises Low Noise Amplifier (LNA) concept was introduced. These are the building blocks of Radiofrequency systems. LNA is an Electronic amplifier that amplifies (very) low power signals without any degradation in Signal-Noise ratio (SNR).

The designer selects less noisy components, Circuit topologies, and Operating points that minimize the additional noises. The minimized noises should be balanced with further design goals of matching impedance and Power gain.

The essential specifications of LNA are Gain, Noise Figure, Linearity, and the max. The input of RF. High amplification at the initial stage of the amplifier results in less noise. This is made possible by selecting transistors like JFETs (Junction Field Effect Transistor) & HEMTs (High Electron Mobility Transistor).

1). What kind of amplifiers can amplify lower strength signals?

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2). LNA’s are placed at _______?

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3). LNA is a ____ amplifier?

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4). What is the purpose of LNA?

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5). LNAs must be kept closed to _____?

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6). __________ is added to the signal received in Low Noise Amplifier (LNA)?

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7). What in LNA restricts the sensitivity of receivers?

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8). What type of models prefer Non-linear Mixing?

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9). What determines the LNA’s efficiency?

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10). LNA must have low______?

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11). What should be the required range of Gain?

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12). What are the various requirements of LNA?

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13). What should be the sensitivity for LNA?

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14). Why the impedance at source matched to the impedances at input in LNA?

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15). What topologies for LNA are chosen for low impedance at source?

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Low Noise Amplifier LNA MCQs for Interviews 

16). What impedances of source use common emitter topology?

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17). What is the appropriate topology if the resistance at source is high in LNA?

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18). What is meant by Source Pulling?

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19). How the topologies are classified in LNA?

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20). What are the various architectures of LNA?

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21). What are the various topologies for LNA Narrow band?

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22). ________ topology degrades the Noise figure in LNA?

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23). How the matching is done in LNA’s Resistive shunt-feedback?

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24). Impedance at input behaves as ______ circuit in Inductive Degenerated topology of LNA.

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25). Which LNA architecture has small Noise figure?

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26). What is IP3 in LNA?

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27). What is the need to improve Linearity of LNA?

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28). What are the popular active devices used in LNA?

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29). Which active devices in LNA generates less noise?

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30). What are the advantages of Ga As pHEMT over si Ge?

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Low Noise Amplifier LNA MCQs for Exams

31). For what applications Ga As pHEMT is chosen?

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32). Why si Ge LNA are preferred?

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33). Dynamic range is limited in _____ LNA?

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34). Why SiGe LNA’s are less costly?

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35). SiGe LNA’s are appropriate in _______ applications?

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36). Why the elements are limited in between input of LNA and antenna?

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37). Greater the reverse isolation makes a way for _______ in LNA?

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38). What is required for less Reverse isolation LNA?

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39). What is the major drawback of using Shunt-Feedback topology in LNA?

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40). Input matching is complex in _______?

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Low Noise Amplifier LNA MCQs for Quiz

41). Why filters are placed prior to LNA?

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42). Given Conditions are Γ0 = 0.485 angle 155 degree Rn = 6 ohms NFmin= 2 dB,NFi= 4 dB,Zo=50ohms, Ni =0.246. Find the radius RFi?

Hint
43). Given Conditions are Γ0 = 0.485 angle 155 degree Rn = 6 ohms NFmin= 2 dB,NFi= 4 dB,Zo=50ohms, Ni =0.246. Find the Noise Figure?

Hint
44). In receiver circuit, LNA is placed between ________ & _________?

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45). Given Conditions are Γ0 = 0.485 angle 155 degree Rn = 6 ohms NFmin= 2 dB,NFi= 4 dB,Zo=50ohms, Ni =0.246. Find the center CFi?

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46). What type of amplifier control Feed line losses?

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47). What are the benefits of using LNA?

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48). What enhances the SDR’s performance?

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49). Which amplifier is known as the building or the essential block of Communication systems?

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50). What type amplifier preferred in satellite communications at receiving ground station?

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