Enough of filters. Lets now look at the simple amplifier model in figure 3.14
   
 
Figure 3.14:  A simple amplifier model.
  
 
Notice that   is with respect to ground while
  is with respect to ground while
  is a voltage difference. 
For a typical operational amplifier
  is a voltage difference. 
For a typical operational amplifier   at
 
at   .
As
 .
As   ,
 ,   due to internal 
capacitance, ie. the amplifier behaves like a low-pass filter.
  due to internal 
capacitance, ie. the amplifier behaves like a low-pass filter.
  
 
where   is the transfer function of a low-pass
filter.
  is the transfer function of a low-pass
filter.
 
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