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Reg UAF42 ic

Paranichandar Paramasivam
Prodigy 120 points
Other Parts Discussed in Thread: UAF42

Hello,

I am using  a UAF 42 ic for 60 hz low pass notch filter.  i have taken the circuit from the application notes document..

i have attached the circuit.  the problem with the circuit is that when i give a input of any frequency from 10 to 100hz. with amplitude 7v, i got a constant output volt of 12 v.  I didn,t used the pin V-. as i shown in fig

Please suggest us.

  • 0
    TI__Genius 12325 points

    Your schematic was not attached to your post, please try to attach it so we are better able to assist you. However, V- must be connected to a power supply voltage or ground to ensure proper operation of the part. 

  • 0 in reply to John Caldwell
    Prodigy 120 points

    i have attached the schematic here. Please find the file attachment.

    Thanks,

    Paranichandar.

  • 0 in reply to Paranichandar Paramasivam
    Prodigy 120 points

    Hello Mr. John

    I have checked the output of the circuit by connecting negative voltage(-14v)  input to the pin V-, still i was not able to get the filtered output for 60hz. If i give the input signal of any frequency with amplitude of TTL logic  i get only constant output voltage of 7V in the pin V out

  • 0 in reply to Paranichandar Paramasivam
    TI__Genius 12325 points

    First, I would suggest replacing the UAF42 with an unused part to ensure that it is not damaged. Again, the V- must be connected to a negative supply voltage or ground to ensure proper operation of the part. If the circuit behaves the same after replacing the part I would suggest verifying the values of all external components with a meter and also verifying the connections on your PCB. Another measurement which would be useful is the output voltage of the UAF42 when the input is connected to ground. With an input of 0V, the output should be very close to 0V as well. A significant DC offset at the output would indicate either the part is damaged or the circuit is not configured correctly.