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choosing the right semiconductor

billybob

Active Member
I'm trying to find a semiconductor (npn is preferred) that can handle high frequency in the range of 20khz and as much current possible in the to22 package.
I will attach a heat sink to the transistor. It will be used to drive a small high voltage transformer.

Thank you,
ben
 

Nigel Goodwin

Super Moderator
Most Helpful Member
20KHz isn't high frequency, in fact it's VERY low frequency as far as transistors are concerned.

Do you mean TO220?.

If you're wanting high current them look at FET's there are some MASSIVE TO220 FET's available - one is rated at 220A.
 

danadak

Well-Known Member
Most Helpful Member
You need to describe how transistor is driven. Using a MOSFET if the interface meant for bipolar
could cause problems, and vice versa. Is it a PWM interface or simple on / off switch type of drive ?
As well type of load, inductive, resistive, and voltage rating needed, etc... Power devices have to be
chosen over a number of design criteria, not in the least SOA considerations.


Regards, Dana.
 
Last edited:

billybob

Active Member
20KHz isn't high frequency, in fact it's VERY low frequency as far as transistors are concerned.

Do you mean TO220?.

If you're wanting high current them look at FET's there are some MASSIVE TO220 FET's available - one is rated at 220A.
Yes TO220 is what I meant. I’m mostly looking for one that has a low internal resistance so it doesn’t require a huge heat sink.
 

billybob

Active Member
You need to describe how transistor is driven. Using a MOSFET if the interface meant for bipolar
could cause problems, and vice versa. Is it a PWM interface or simple on / off switch type of drive ?
As well type of load, inductive, resistive, and voltage rating needed, etc... Power devices have to be
chosen over a number of design criteria, not in the least SOA considerations.


Regards, Dana.
I need two for an astable multi oscillator type circuit. The transistors (or mosfets) will be used as simple switches. I hope that answers your question.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I need two for an astable multi oscillator type circuit. The transistors (or mosfets) will be used as simple switches. I hope that answers your question.
Those crude multi-vibrator circuits are generally pretty crap, very inefficient, and need much larger heat sinks because of it. They are also renowned for their unreliability, as the 'design' is so poor.
 

billybob

Active Member
Those crude multi-vibrator circuits are generally pretty crap, very inefficient, and need much larger heat sinks because of it. They are also renowned for their unreliability, as the 'design' is so poor.
What circuit would you recommend for switching a small high voltage transformer then?
 

billybob

Active Member
I’m trying to produce steady arcs about a half an inch to an inch gap from parts and a circuit that take up the least amount of space possible.

I don’t see the link you mentioned above
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Well damn - lost the link somewhere? :D

It was here:


However, now you've mentioned what you're looking for, try this link:

 

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