Transistors proprieties

This is a very interesting page for the knwoledge of transistors.
http://101science.com/transistor.htm

This is a really good video for the transistor comprehension.

• Code reference/ characteristic / metal package/ amplifier - switching / 

- Small signal

• 2N2219  / NPN / TO-92/ amplifier - switching
• 2N2222  / NPN / TO-92/ 
• PN2222A / NPN / TO-92/ 
• 2N2907  / PNP / TO-18/ 
• 2N4401  / NPN / TO-92/ 
• 2N3904  / NPN / TO-92/ 
• 2N3906  / PNP / TO-92/ 
• 2N4403  / PNP / TO-92/ 
• 2N5401  / PNP / TO-92/ 
• 2N5551  / NPN / TO-92/ 
• 2SC945  / NPN / TO-92/ 
• BC327  / PNP / TO-92/ 
• BC337  / NPN / TO-92/ 
• BC338 / NPN / TO-92 /
• BC546 / NPN / TO-92 /
• BC547 / NPN / TO-92 /
• BC548 / NPN / TO-92 /
• BC549 / NPN / TO-92 /
• BC550 / NPN / TO-92 /
• BC556 / PNP / TO-92 / 
• BC557 / PNP / TO-92 / 
• BC558 / PNP / TO-92 / 
• BC807 / SMD-PNP / SOT-23 /
• BC817 / SMD-NPN / SOT-23 /
• BC848 / SMD-NPN / SOT-23 /

- Small power

• 2N1711 / SMD-NPN / SOT-23 /
• 2N2369 / 
• 2N2907 /
• BC107 /
• BC108 /
• BC109 /
• BC140 /
• BC237 /
• BC238 /
• BC239 /
• BC307 /
• 
  

- Power

Buck Converter & Arduino

Description:
The Buck converter is a step-down DC/DC converter in power electronics.
http://en.wikipedia.org/wiki/Buck_converter

Applications: 

- Battery charger (mobile, radio, ....) 

- Control load

Schematic: 

Components:
- Transistor
- Inductance
- Capacitor
- Diode
- Arduino (controller)
- Power source

In protoboard:

Arduino code:

The first code is like a motor speed code. 

Code 1

The second code use the delay for the on period  and off period.

Graphics whit the oscillogram:

* The real power source is a 8V DC.

Graphics with code 1, Transistor switching (Green), Output voltage (Red)  

Graphics with code 2, Transistor switching (Red), Output voltage (Green)