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H.A.B said:Thanks for your note, but isn't the 22k risistors and the LEDs enough ?
(sorry, but I'm not an expert, I'm just a hobbier !)
H.A.B said:Thanks again. what about changing the supply voltage. Let it be just 3 volts.
is the problem still exist? (considering "Cry Wolf" asked for the simplest circuit)
This will seriously screw up the circuit. The capacitors need to discharge through the base resistors. With shunt diodes added, the frequency will be much higher. Collector risetimes will also suffer.Nigel Goodwin said:6V or lower would be fine - it's around 7V that transistors start to break down. For higher voltages just add 'catching diodes' across the base and emitter of the transistors, cathode to the base (for NPN transistors). These limit the reverse Vbe to 0.7V.
Nigel Goodwin said:Serious error in that diagram! - you should have protection diodes on the transistor bases, with a 9V supply it's likely to cause reverse Vbe breakdown of the transistors.
Well, OK, but a novice might want to be aware that the circuit posted above oscillates at about 8Hz with the diodes in series with the bases, and about 39Hz with them shunting the bases. Also, in the latter case, peak repetitive collector and diode currents can exceed one amp, depending on transistor beta - speaking of dead BC108s.Nigel Goodwin said:All three suggested methods work - and all three alter the timing, but better altered timing than a pile of dead BC108's!.
Transistor manufacturers publish datasheets that list the absolute maximum voltages and currents allowed for each transistor. The reverse-biased emitter-base junction of a BC108 transistor has a max voltage rating of 5.0V.Cry_Wolf said:Can you explain a little bit