multivibrator ringing ?
 

Hi,
I have built this multivibrator :
http://www.interq.or.jp/japan/se-inoue/e_ckt5_1.htm

I wanted to use it to test amplifiers.But in scope , i see some small ringing at edges of square wave! I used 100nF supply bypass cap directly at ICs pins.PSU is regulated with 7805.there is no supply noise. I thought it was my error , so i built the same cirtuit again , but the problem remains.
How can this be fixed ?

Best regards,
Lukas.

Re: multivibrator ringing ?
 

Try better bypassing, for example remove that 100nF and use only 220uF electrolytic cap. and/or use cmos-version of 555, LMC555 for example.

And, have you calibrated your scope probes?

Either follow mzzj advice or solder the 100nF directly on the leads of the electrolytic. You have just discovered that 100nF decoupling capacitors are a two edged solution.

Where are you putting the ground line of the 'scope probe? The ground reference is critical; if it's a significant length from pin 1 of the 555, you'll get wiggles in the waveform... You could also put a little bit of resistive load on the output to ground to see if that clears up the ring... (i.e. 100 ohms?)

Cheers