15. RF Transistor Part Two

Part Two shows a selection of different RF transistor curve characteristics.
Especially the RF transistor datasheets don't show these curve characteristics in necessary detail.


Different RF Transistor Types on the Curve Tracer

   
Transistors under Test , some RF transistors and one standard transistor for comparison.
          

xxxx Transistor Curves


These are the transistors used in the diode-bridge-part-four - I soldered them out  to build-up a better diode bridge.


   

   


All curves done with a Collector Current 1mA/DIV and a Collector-Emitter Voltage 0.5V/DIV.
Base current inreases in 5µA steps. These resistors showing curves with a DC Gain of approximately 100. 



   
                                              Left photo 0.5V/DIV                                                                                                      Right photo 2V/DIV

This is another xxxx transistor, the one soldered on the small PCB. This transistor shows strange curves, no idea what happened.
At a 12 volt  Collector Emitter Voltage the transistor curves begins to breaktrough.




   
                           Left Photo - Basis Emitter Diode Forward                                                                  Right Photo - Basis/Collector Emitter Diode Forward

The Base Emitter diode behaves like excepted, but in common Base-Collector diode the curve looks funny. The right curve is highly dependend from the way you are touching the transistor with your fingers or moving the curve tracer wires.  Touching the transistor in a capacitive way the curve changes more and more to show normal diode curve behaviour. This is an indicator layout using a a common base collector diode will a be serious matter. At the moment I have no good explanation for the reasons.




   
                              Left Photo - Base Emitter Diode Reversed                                                        Right Photo - Base/Collector Emitter Diode Reversed

Breakthrough at 6 volts. Device can be used as diode for low reverse voltages.



xxxx Transistor Curves 

The xxxx is a xx volt, xxmA transistor.

   
The xxxx shows an breakthrough at 6 volts, has a DC Gain of approximately 150.


   
                                     Left Photo - Basis Emitter Diode Forward                                                   Right Photo - Basis/Collector Emitter Diode Forward


The Base Emitter diode behaves like excepted, but in common Base-Collector diode the curve looks funny. The right curve is highly dependend from the way you are touching the transistor with your fingers or moving the curve tracer wires.  Touching the transistor in a capacitive way the curve changes more and more to show normal diode curve behaviour. This is an indicator using a common base collector diode in a layout will a be serious matter. At the moment I have no good explanation for the reasons.





   
                                 Left Photo - Base Emitter Diode Reversed                                                        Right Photo - Base/Collector Emitter Diode Reversed


At about 5 volts the reversed diode start to breaktrough. The common Base/Collector diode shows again a strange curve. Also this diode shows more and more normal curves  when you start touching the DUT in a capacitive way with your fingers. But in this case the curves are not so much dependend from parasitic capacitances like in the forward connection.

The maximum base current for this transistor is specified with a  2mA DC current, under the curve tracer the base current can be adjusted higher, because it's not a DC load. and the transistor should be still in the SOA. It's not the first transistor destroyed on a curve tracer.




xxxx Transistor Curves 

The xxxx is a xx volt, xxx mA standard transistor.. This curves are shown because of a type comparison.


Breakthrough appears on higher voltages, DC Gain 180.


   
                                Left Photo - Basis Emitter Diode Forward                                                   Right Photo - Basis/Collector Emitter Diode Forward



   
                               Left Photo - Base Emitter Diode Reversed                                                        Right Photo - Base/Collector Emitter Diode Reversed

With the standard xxxx transistor everything behaves like excepted. Breakthrough at 8 volts.



xxxx Transistor Curves 

The xxxx is a xx volt, xxmA transistor.

   

   

 

   
     

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