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Is it really necessary to use 2222A transistor to make mini tesla coil?

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dante_clericuzzio

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I have seen some circuit always use 2222A transistor to make the tesla coil..is this transistor is the only one works..why others like S9018, C3355, C945 cannot use? please advise what is the main reason the 2222A because i need to know this in order to buy it otherwise i buy the wrong transistor
 

The 2222A is an old-generation switching transistor, starting life as a metal can (TO-18) transistor in the 1960s. It's one of those products that proved to be suitable for a variety of applications and continues to be widely available, especially as the TO-92 plastic version. It has higher current and voltage ratings and lower saturation voltage than the other types you mentioned. These properties are important when dealing with anything other than very low power levels.

Another factor is that, even when there are several different types that can be used for a given task, designers tend to use the one they are most familiar with and/or are most easily available.
 

Another thing i want to know about the tesla coil some people will use 9 volt battery and using resistor 22 kOhm...to the base of the 2n2222A transistor...why they do this and what is the calculation involve
 

You would want to post (or link) a schematic so that we know what you are talking about.

For the time being: Expect that any small transistor with similar voltage and current rating will work in place of 2N2222.
 

With a 9V battery then a series base resistor value of 22k is much too high. It makes the base current only (9V - 0.7V)/22k= 3.8mA. The datasheet for the 2N2222A and most other little transistors shows that for it to saturate well its base current should be 1/10th its collector current. Here its collector current is probably a lot more than only 38mA.
 

A simple self-oscillating inverter can't be designed for Ib/Ic = 1/10. The collector current rises until it's limited by the actual current gain. If Ib is too high, you kill the transistor.
 

CataM said:
I bet is this one:

- - - Updated - - -

Click to expand...

Yes this is exactly it..

With a 9V battery then a series base resistor value of 22k is much too high. It makes the base current only (9V - 0.7V)/22k= 3.8mA. The datasheet for the 2N2222A and most other little transistors shows that for it to saturate well its base current should be 1/10th its collector current. Here its collector current is probably a lot more than only 38mA.
Click to expand...

But the circuit works well as shown in most youtube video

A simple self-oscillating inverter can't be designed for Ib/Ic = 1/10. The collector current rises until it's limited by the actual current gain. If Ib is too high, you kill the transistor.
Click to expand...

I don't understand this please kindly explain more
 

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