[SOLVED] Astable Multivibrator Problem

[hobbyckts]

Small things hurt a lot...

A simple multivibrator using 555 timer IC giving me unstable clock pulses. Some one please explain me why it is?

RA & RB values are 750\[\Omega\]

Capacitor value is 1nF

The frequency is toggling between 300KHz to 750KHz. I have even used a diode between discharge and trigger(threshold) pin.

 

[betwixt]

Those are quite low values and they will sink significant current, they may be making the supply unstable.

Try increasing the resistor values and adjust the timing capacitor to restore the frequency you want. Also add a capacitor to ground from pin 5 and make sure you have suitable capacitors across the supply pins.

Brian.

 

[Vbase]

Small things hurt a lot...

A simple multivibrator using 555 timer IC giving me unstable clock pulses. Some one please explain me why it is?

RA & RB values are 750\[\Omega\]

Capacitor value is 1nF

The frequency is toggling between 300KHz to 750KHz. I have even used a diode between discharge and trigger(threshold) pin.

The NE555 (transistorized) max frequency is 100KHz. The cmos version can oscillate at max 500KHz.

 

[hobbyckts]

Thanks for the help guys. solved by replacing with higher value of resistors.