1.What effect did changing CE from electrolytic to non-electrolytic have? Do a l
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Question
1.What effect did changing CE from electrolytic to non-electrolytic have? Do a little research to find a possible explanation. Write 2-3 sentences summarizing it and include your source, you may not use your book or Wikipedia as a source.
2 Explain how each R, L, C component of the Tank node effects the amplifier using the formulas given in class. *** Hint - ideally each component has a unique effect, use the formulas to explain
***Note R6 is the output impedance of the function generator*** Ct Lt Rt 680pF 47 270 Rb1 1 0000 Q1 V2 12V R6 50 2N 3904 1HF RL V1 25mVpk 1kHz 0° Rb2 1800 CE 10uF Re 82 Figure 1: Tuned Amplifier CircuitExplanation / Answer
1. The emitter bypass capacitor is responsible for shorting the emitter of the transistor at the frequency of interest and thus 'bypass'ing the emitter resistor Re so that we get more ac gain, whereas the emitter degeneration resistor Re is meant to reduce the dc bias current. Electrolytic capacitors have high lead inductance as compared to the ceramic ones. The inductance of a typical surface mount ceramic capacitor is 0.5nH, while the inductance of an electrolytic capacitor is 15nH. Thus depending upon the frequency of operation, this lead inductance will present a high impedance which will defeat the purpose of the bypass capacitor. Thus an improvement in the gain can be observed by replacing an electrolytic capacitor with a ceramic one.
2. The parallel RLC circuit forms a parallel resonant circuit, where the resonant frequency is 1/(2*pi*sqrt(LC)).
Since frequency is inversely proportional to L and C, the increase (decrease) in L or C will result in the decrease (increase) in the tuned frequency of the amplifier.
At the resonant frequency the net impedance of the tank circuit is R and thus the output voltage is proportional to the value of R. Thus increase in R will result in increase in the gain of the amplifier.
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