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Active Filter Troubleshooting

The animation below shows the effect of varying C1 and C2 from .001 uf to .1uf on the frequency response of the Active Low Pass Filter. Use curve below for baseline information.

 

 

Troubleshoot Circuit Below

Determine the component failure which caused Fault 1 through Fault 3 shown by below plots. Select faulty component from list below. Hint: Do not give the same answer (1 - 6) twice.

            1. C1 open
            2. C2 decreased in capacitance(decrease less than 50%).
            3. C1 Leaky.
            4. C2 Leaky.
            5. R1 open.
            6. R2 open       

            ANSWERS AT BOTTOM OF PAGE

 

 

 

 

     ANSWERS AT BOTTOM OF PAGE

 

 

 

 

 

     ANSWERS AT BOTTOM OF PAGE

 

 

 

 

     ANSWERS BELOW

 

Fault 1 Answer

No.2- C2  decreased in capacitance. (Failed C2 = .006uf )

 

 

 

 

 

ANSWERS BELOW

 

 

 

 

 

 

 

Fault 2 Answer

No.1- C1 Open
Note that with C1 open the circuit becomes a simple RC or first order   filter with an op-amp voltage follower.  This results in a reduced  roll off rate of about 6db per octave

 

 

 

 

 

ANSWERS BELOW

 

 

Fault 3 Answer

No.4- C2 Leaky (Rparallel= 12k)

The voltage divider formed by Rparallel , R1, and R2 causes the normally unity low frequency gain of this circuit to be reduced.