This circuit will "consume" less than 100mA, so any power source that can deliver this sort of current (@9V) , or more, will be OK ..
Just remember to add a current limiting resistor in series with both diodes ..
Hi,
Nine volt supply rating really should not matter, but the basic circuit may need some current limiting resistor at the collector of BC546. Also, base resistance of about 1.2 k should suffice if collector current is limited to around 200 mA peak.
Regards,
Laktronics
I suggest putting a 56ohm resistor at collector, and changing the base resistor to 7.4k-ohm. Then the current of LEDs is limited to 100ma, and the transistor gets its saturation level very well.
In this way, the consumption of your circuit lowers ,and you have no problem with your any power supply, even a weaker one.
Good Luck.