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I am trying to make a square wave generator using 555. I need a 16kHz 0-5V square wave. I have referenced this site (%50 duty cycle). When the frequency increases, the square wave have distorted gradually. This is my circuit for 16 kHz, 741 is used for buffer.

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My output voltage is;

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When i set R3 to 450Ω to decrease frequency to 1.6 kHz, the response is better;

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Do you have a idea to get a better square wave for 16 kHz in this circuit? Thank you so much.

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  • \$\begingroup\$ If 0 to 5V is the output swing that you need then you won't need to buffer the output from the 555. On your top waveform/trace I think the distortion is from your scope leads, not the actual signal. Check your scope ground clip and use a X10 probe if you have one. \$\endgroup\$ – Entrepreneur Jul 28 '17 at 10:36
  • \$\begingroup\$ Thank you so much. That was LTSpice simulation result actually. I was thinking that buffer can increase the output current a little bit. When i don't use the buffer, distortion is still there. \$\endgroup\$ – layout789 Jul 28 '17 at 10:38
  • \$\begingroup\$ I overlooked the fact that this implementation feeds the 555 output back into the analog components, which probably could cause some distortion on the output. The square wave output could be cleaned up with a Schmidt trigger (like a 74LS14) or a comparator rather than the 741 \$\endgroup\$ – Entrepreneur Jul 28 '17 at 10:58
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    \$\begingroup\$ The 555 can drive about +/-200 mA. The 741 can drive about +/-25 mA. How exactly were you hoping to increase the output current? Anyway, keep the larger value for R3, and decrease C1 to 100 nF. \$\endgroup\$ – Dave Tweed Jul 28 '17 at 11:04
  • \$\begingroup\$ I think you mean '741 was misused as a buffer' \$\endgroup\$ – Neil_UK Jul 28 '17 at 13:18

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