How To remember the direction of PNP and NPN Transistor. One of the Easiest way. 

 FINDING THE BASE  and determining NPN or PNP

Get an unknown transistor and test it with a multimeter set to "x10"
Try the 6 combinations and when you have the black probe on a pin and the red probe touches
 the other pins
 and the meter swings nearly full scale, you have an NPN transistor.
 The black probe is BASE
If the red probe touches a pin and the black probe produces a swing on the other two pins, you have a PNP transistor.
 The red probe is BASE
If the needle swings FULL SCALE or if it swings for more than 2 readings, the transistor is FAULTY.

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How many types of Multimeter.

                                                       DIGITAL and ANALOGUE

A Digital Multimeter has a set of digits on the display and an Analogue Multimeter
 has a scale with a pointer (or needle).

You really need both types to cover the number of tests needed for designing and repair-work.
  We will discuss how they work, how to use them and some of the differences between them.

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How to learn basic Electronics ?

              How to learn basic Electronics ?
    
  Basic electronic circuit symbols

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How is made 555 timer.

                                                     555 Timer IC
 
    The 555 Timer is the one of the most versatile linear hybrid Integrated Circuit IC which is used in variety of pulse generation, timer and oscillator applications. In 1972, signetics Corporation first introduced this device as the SE/NE 555.
Commonly 555 has 3 operating modes 555 Timer
Now a days it is manufactured by many companies in bipolar and in low power CMOS. It is widely used in electronics circuits as it is very simple and cheap method to produce accurate and highly stable time delays. It can be used for various timing applications from microseconds to hours range and can source or sink up to 200 mA current.
When the output of 555 is HIGH current is sourced from the IC and when the output is LOW 555 is sinking current. It can source or sink current up to 200mA. If the load requires more than 200mA we can connect an external driver transistor for that.

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