Diodes and Transistors

Diodes

Today im going to talk about diodes first.

There is a few components which is getting called Diodes. Like Diodes, ZenerDiodes and L.E.D. ( Light Emitted Diodes).

Normal Diode has a voltage drop of 0.6v, 0.538v from a practical. And if you have a look on the picture, a silver line on the diode means a negative side and a black side is a posetive.

On the practical i had to find out the voltage drop of the diode, so i did switch my multimeter on a diode selection and used my posetive and a negative probes to connect to the diode. By doing that, i did found a reading of 0.538v, thats a voltage drop of it. When i have connected my probs at other way, i had a reading of .OL. That means, no voltage going this way and cant get a reading.
Thats a forward voltage drop of diode.


L.E.D. ( Light Emitted Diode) has a voltage drop of 1.7v, 1.734v from a practical. It has two legs, one is a short one, which is a negative and a longer one, which is a posetive. Inside it has a small pin, which is a posetive and a bigger flat pin, which is a negative side.

On practical i have used a small board, to place my components so i can test them and use them. Ive tested one of the L.E.D.s. By switching my multimeter to the Diodes mode and placing the probs on the L.E.D.d Legs. Ive got a reading of 1.734v, thats a voltage drop of it. And when i did connect my probs the other way, the reading was .OL. So cant get the reading this way.
The L.E.D. has a higher voltage drop then a diode and that means that it has a lower current flow.


Zeners diodes is the same as a normal diodes but has a slightly higher voltage drop of a 0.8v. Zener diodes allows the current to pass in one direction and reverse position. It used to protect the circuit from a high voltage surges and to regulate the voltage. The voltage drop of the zener diode can be even 5v. It does depend on it and for what voltage it is made.

Reverse the polarity of the zener diode.
When ive connected the Zener Diode to test it, the measurement was 0.86v. The zener diode allows the current to flow but it does not regulates it. When you put it in a reverse position. It acts like a normal diode.

Cathode = is a NEGATIVE -
Anode = is a POSETIVE +
Sides of the diodes.

I had no problems with that and it was easy to understand, the only fault i had with a zener diode, plugging it in a wrong way in my circuit on the board, Which end up of my resistor to heat up and smoke a little. After that, ive started to knew what and how to do it right.
At this subject, ive learned about a different types of diodes, their voltage drops and function. But the main one, is how to indentify which ine is what and what side is a negative and which is a posetive.







Transistors

There is a few types of transistors and now i will write some information of my theory and practical lessons i have done in class.

BJT- Bipolar Junction Transistor

Here is some easy ways to remember a right transistor.

PNP is Park Now Please
NPN is No Park Now

The NPN Transistor has a Base, Collector and an Emitter. The arial will be down on an emitter side. To measure the voltage drop and to find out which transistor is it. There is a way of doing it with a multimeter. By using your probs and place it on one or two legs of the transistor. Each transistor has three legs.
So NPN has a negative which is a collector, posetive which is a base and a negative which is an emmiter.

The PNP has a collector, base and an emitter, same way to test it as a NPN transistor but the collector is posetive, base is a negative and an emitter is a posetive.

You always have to connect a resistor on the base of the transistor. Collector side will have a smaller voltage. And a Emitter side will have a higher voltage.

The voltage the transistor needs to be operating is 0.6-0.7v.

On my practical, i had to find a voltage drop of the NPN transistor, which was 0.754v because the transistor has a diode inside of it, which needs a voltage of 0.6-0.7v to be operating.

Transistors has three different types of the Region:
Saturation region is when the transistor is fully on and operating the current levels.
Cut off region is when the transistor has hardly any current or none at all.
Active region is when the transistor is operating in a middle between the saturation and a cut off regions.

Thats a better description of how to indentify the terminals on a Transistor.
You have to find the base, set your multimeter to the siodes function mode. Then play around with the probes between three legs of the transistor. When you get a reading between one pin to both other two pins. This pin will be your base, if your red probe on the base, thats NPN one and if its on a black probe, thats a PNP one.


If there will be more current going thrue the base, it will be more in a saturation mode. But if there is less current thrue the base, it will be more in an anplification mode, so in a cut off region.

I found no faults with the transistors, as it was easy to understand and to learn how and what they does. The only mess around is to find what leg is what. For that, you will have to use a multimeter. Any one will need to use it, as if you connect the legs in a wrong way, the circuit will not work good or even not going to be working.

If the transistor is getting shorted, nothing will happen to the transistor when you shorten C with E, but components around it may be damaged due to unlimited currents (short means 0 ohm).
However, when you release the short and damage has occurred to a components connected to it, there is a good chance that it also will be damaged.


All photos have been taken of google images by tiping. Diodes and Transistors. Here is some links:

http://ram-e-shop.com/oscmax/catalog/index.php?cPath=141
http://www.markallen.com/teaching/ucsd/147a/lectures/lecture3/5.php
http://www.google.com/imgres?um=1&hl=ru&biw=1280&bih=600&tbm=isch&tbnid=zVvYRRhpPtMypM:&imgrefurl=http://www.simplemotor.com/tmotor.htm&docid=UO6dbGgE4OdEYM&imgurl=http://www.simplemotor.com/images/transistors.gif&w=393&h=193&ei=OolvT9v0EqqOmQXEwdWkBg&zoom=1&iact=hc&vpx=919&vpy=328&dur=190&hovh=154&hovw=314&tx=181&ty=95&sig=101673499850352112935&page=1&tbnh=83&tbnw=168&start=0&ndsp=18&ved=1t:429,r:17,s:0
http://www.reuk.co.uk/What-is-a-Transistor.htm