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2n2222 or Bc109 as switch

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mehboob_iiui

mehboob_iiui

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2n2222 switch

I want to use anyone of these two transistors as a switch to control a relay , please provide some assistance ...
 

2n2222 as switch

just take care that the Vbe switches from below 0.7V to saturation to get the relay to turn on.... connect the relay in collector or emitter...
 

2n2222 as a switch

The 2N2222 is better as a switch. It has a higher current rating and also, although not be relevant to your application, faster switching times.
Don't forget the diode across the relay's coil, or you will fry the transistor.
Save the BC109 for that low-noise preamp you will one day build.
 

2n2222 switch circuit

simple switch circuit u can build with just one resistor & one transistor like 2N 2222.
 

bc109 as switch

**broken link removed**

Put your relay coil as load for figure 2, replace 2n3904 with 2n2222. R2 may not be needed. Make sure you don't draw more power than what the transistor is rated for.
 

transistor 2n2222+switch

both transistors are good, with good current rate at the base of any transistor and voltage between base and emitter more than 1 volt! to ensure 0.7v at Vbe, it will be ok
 

relay diode bc109

The webpage given by rowokii is a good page with a bit confused explanation. However, since using a transistor as a switch is easiest type of designing a transistor circuit, so you can gain from that page.

In term of switching behavior, 2N2222 is better, but for the purpose of switching the relay, it means that at very low frequency, both are good choice, of course if their collector current is high enough for you to drive your relay as well as your drive stage can provide the enough current to drive these transistor.

nguyennam
 

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