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How to choose the model number of the transistors in this circuit?

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Junior Member level 2
Apr 14, 2011
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Could you help me choose the model number of the transistors in this circuit?The voltage is large.

Thank you very much.

"this circuit" doesn't describe your circuit and if your intention was to attach a schematic you didn't so you have to post it again.


I am sorry,but I can not insert the image.

Let me try it again.

---------- Post added at 06:48 ---------- Previous post was at 06:46 ----------

I can not click the“insert image”.

Instead of quick reply press go advanced at the end of the page, there you will see an attachment button which opens a dialog to attach a picture, file etc.
If you want to add a link to an image there is a add image icon at the menu over the message, this exists in both quick reply and advanced.


This is the picture.

Thank you very much.

From what I can tell the 2sa1015 is only rated at 40v, so wouldnt withstand the volatge shown on your schematic.
At lower voltages I'd use a bc559 for the 2sa1015, and a bc549 for the other, but be warned these devices wont stand 230vdc.

Voltage rating is one thing, power rating and providing suitable heat sinks another. According to the circuit dimensioning, Q1 and Q4 can be loaded with up to 2 W, depending on the function generator setting. Did you take this into consideration? If there's no reasonable purpose of operating the amplifier at this rather high power level, you may want to reassign some resistor values. Complementary transistors with sufficient voltage rating (and also power capability, if actually needed) can be found e.g. in the Onsemi portfolio.

Also Q4 misses a base-emitter resistor to absorb Q3 leakage currents.

The maximum voltage we want to get is at least 100V,so where can I get the property transistor?

By the way,Q2 and Q3 are the same transistor,the supply voltage can lower than 230V.

How about 2SA940 and 2sa3039?

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The selection of maximum rated Voltage and maximum rated current, is not enough to ensure proper wattage.
We must consider the Safe Operating Area (SOA) wich is defined in grafical format at datasheets.
That power is also restricted by switchin frequency.


Thank you,everyone.

Dear FvM,Thanks for your advise,but now I can ont get the MJE340 and MJE 350,how about NTE39 and NTE157?

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Thank you very much.

Best regards.

The NTE devices are very similar to MJE as far as I see.

Please allow me to ask another question,if I change the 230V to 200V or 100V,do I still need to change the value of the resistors?

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