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What are the 4 pins in RF transistor for?

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countmybones

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Hi, I often encounter RF transistors with 4 pins instead of the usual 3 pins. 2 of the pins are emitter pins. Why are the 4 pins? How do I use the 2 emitter pins?
 

Re: 4 pins RF transistor

In most cases emitters are connected to GND, so you can connect either of themor both. In power transistors you will use this additional emitter pin to simply despatch heat .. cool down that b-----d ..
Regards,
IanP
 

Re: 4 pins RF transistor

Hi

I guest that fourth pin is used for substrate bias, and avoid parasitic diode between p-n junctions. This can be shortcutted to emitter when it is a tail transistor, I mean, when emitter pin must be wired to the maximun or minimun bias point (according transistor type).
 

Re: 4 pins RF transistor

Second emitter pin is usually found at rf transistors. Its purpouse is when connected parallely to ground to lower emitter pin inductance and thus increase gain at higher frequencies.
Fourth pin at rf transistors, if the transistor case is metal one, is the case pin and is usually connected to ground.
 

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