I tried to find datasheets for BC331 and BC541 to compare them with BC547.
Can I replace BC331 / BC541 with BC547?
NPN, 60v, 30 mA, hFE= 125, Ft = 100 MHz, TI, low noise, TO92
BC541: Does not seem to be a known device.
A BC547 will be a good substitute for most older silicon NPN transistors.
For most small signal transistor purposes I use and recommend the following:
All 45V, typically 0.8A (varies slightly with manufacturer), TO92 or SOT23 Ft = 100 Mhz Hfe (current gain = 250-600, mean = 400.
All these are often available as cheaply as any other transistor available (look around) and have abpout as good a combination of current, current gain and general usefulness as anyhing else going. When you find better cheaper please advise.