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astable multivibrator

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If the supply voltage is greater than 5V the bases of the BJTs need diodes adding to protect them against the reverse voltage generated.
 
There are a few spelling errors.

The capacitors are charged quickly by Rc and discharged slowly by Rb.

As Hero says, the emitter-base voltage (reverse voltage) exceeds the 5V to 6V max allowed voltage of most small silicon transistors.

The typical collector saturation voltage is less than 0.1V, not 0.5V.
 
Yes, thanks I made a mistake about the power supply voltage.
As to saturation voltage you are probbably right but in my school
they sead 0.5V and high current transistors have saturation voltage
of 5 V (if I read the datasheet correctly).
(for example BUX98A for 24A)
 
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The saturation voltage depends on the type of transistor, the base and collector current and the temperature.

The maximum current is only 60mA so there's no need to use power transistors, an ordinary small signal transistor such as the BC548 will do.

Why are the resistor values so low?

I'd divide all the resistor and capacitors by 10 to reduce the current required. If you need a high current output, an extra booster transistor can be added.
 
Yes, sorry I meant multiply the resistor values by 10 and divide the capacitor values by 10.

Another option for high powered devices is to use MOSFETs instead of BJTs but the circuit needs a couple of subtle changes to work.
 
As to saturation voltage you are probably right but in my school
they sead 0.5V and high current transistors have saturation voltage
of 5 V (if I read the datasheet correctly).
(for example BUX98A for 24A)
24A is a lot more than only 60mA in your schematic.
 
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