Frequency Response of RC Coupled Amplifier

  • BJT
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As can be seen from the output frequency plot the gain is constant for a certain number of frequencies. This range is called mid-frequency band. For very low and very high frequencies the gain is almost zero. In mid band frequency range, the coupling capacitors and bypass capacitors are as good as short circuits, but this is not the case at low frequencies. At low frequencies, the capacitance increases to a very high value adn at high frequencies it goes to almost 0. The many coupling capacitors contribute to the low gain at low frequencies. For exxample the input capacitance will be high such that a major portion of the input voltage will drop across it thus reducing the output voltage and hence gaiin. As the frequency of the input signal increases, again the gain of the amplifier reduces. Firstly the b of the transistor decreases at higher frequency. Thus reducing the voltage gain of the amplifier at higher frequencies

Circuit info


Created on: 21 Feb 2013
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