Borber
Joined: 01 Jan 1970
Posts: 1485
Helped: 111
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 24 Oct 2004 18:58 Re: rc coupled amp. |
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Reactance of a capacitor is Xc=1/(2*pi*f*C). It is infinite at f=0Hz and zero at infinite frequency.
At RC coupled amplifiers, in general, we can have different examples. The coupling capacitor and the resistor which follows it and which is grounded form a highpass filter. For passband frequencies it's capacitance should be large enough to present small resistance to signal. In passband can be considered as AC short circuit. At low frequencies, under the passband, it represent high reactance and finally at f=0Hz it's reactance is infinite.
You can consider capacitor a AC short circuit when it's reactance is much smaller than resistance it connect's to or bypasses it and viceversa.
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