TLC04: TLC04 FILTER CUT OFF FREQUENCY ISSUES

Hi Uma,

Your TLC04 schematic shows a 10k resistor, can you please verify the actual value on your PCB?

hi,

  i have changed to 560 ohms for cut off frequency of 200 Hz.

Hi Uma,

OK - thanks for confirming.  Not sure what the issue might be, this is a pretty simple/straight forward device.  Can you send over scope shots showing your clock, along with the input and output signals?

hi Tom,

   now i have changed the resistor to 1K Ohms so the cut off frequency set to 100Hz(nearly) .so at 50 Hz the insertion gain relative to dc gain will be 0 dB. At 50 Hz i could see the drop in peak to peak voltage of the sine wave . i have attached he waveforms at input of filter and also output of filter. please reply asap.

1.output of filter at 50Hz

2.input of filter at 50Hz

below attached is the clock input to filter

Thank you Uma,

By the clock screen shot, you are running at 2.625kHz.  At that speed, your -3dB point would be 2625/50 or ~52.5Hz which seems to agree with the input/output waveforms.  Do you have another signal generator that you could try using as the clock source to verify your desired cutoff frequency?

hi Tom,

 I want to know what is the relation between Clock and the RC values. i have put a 1K pot and kept varying so that i got the resistor value for particular cut off frequency.but to find the exact values what is the relation between them?

Hi Uma,

At the moment, my only source of reference is in the TLC04 datasheet - the formula associated with Figure 5.  I've ordered some samples and plan to look at it a little more since I've never actually used this device myself.  As soon as I know anything, I'll get back to you.