NPN TRANSISTOR

Hi :)

So my friend and I found an easier way of remembering the NPN experiment conections. I still remember searching the web for this experiment a night before my practical exam and I was unsuccessful so I thought of sharing this with you.

Its pretty easy actually :P the red dots show positive terminals while the black ones show negative terminals. The green lines are the ten wires you need to connect in a circuit. The following circuit worked for me and it should work out for you too. In case it doesn’t(sometimes the transistor box is different), I’m not responsible :p so I recommend that you try it once in your lab class.

Please refer to the diagram below(PLEASE SEE THE DIAGRAM IN THE LAB MANUAL WHICH IS TO BE DRAWN ON THE DAY OF THE EXAM AS THIS IS ONLY FOR US TO FIGURE OUT THE CIRCUIT)):

1. Connect the positive of the voltmeter(Vbe) to the positive  of the battery(0-1V) and negative to the negative terminal of the battery.

2. Do the same on the right hand side with the Vc and the Battery(0-10V).

3. Connect the positive of the (uA)ammeter to the positive of the battery and 
negative to the positive of the npn.

4. Connect the positive of the (mA)ammeter to the positive of the battery and negative to the negative of the npn.

5. Then connect the negative terminals of the battery(the ones which are left) to the  2 negative terminals below the npn.

Switch on the power and see if the circuit works. Don’t forget to connect it to a socket and switch on the main switch :P

In a transistor you have 2 voltmeters and 2 ammeters.

For input characteristics:
You keep the voltmeter ‘s(Vc) voltage constant. Eg: 2v and 4v.

Take the Vc as 2V . You can now vary the other voltage(Vbe) by using that variable knob or whatever that is and write down the readings you observe on the ammeter.(uA)

Then repeat this after changing the voltage to 4V.

For output characteristics:

You need to keep the current constant. So first, you use the knobs and get the pointer on the (uA)ammeter on the 40 mark, change the voltage and note down the observations of the changing current in the (mA)Ammeter.

Then get the pointer at the 80 mark, and repeat the steps.

NOTE: you need to vary the current or voltage very slowly and don’t keep the power on for too long as it heats up the circuit and increases resistance.

Sample Observation Table:

Input characterisitcs:

S.no	Vc(V)	Vbe(V)	Ib(uA)	S.no.	Vc(V)	Vbe(V)	Ib(uA)
1	2			1	4
2	2			2	4
3	2			3	4
4	2			4	4
5	2			5	4
6	2			6	4

Output characteristics :

S.no.	Ib(uA)	Vc(V)	Vbe(V)	S.no.	Ib(uA)	Vc(V)	V(be)
1	40			1	80
2	40			2	80
3	40			3	80
4	40			4	80
5	40			5	80
6	40			6	80
7	40			7	80

PLEASE DON’T MAKE THE DIAGRAM ABOVE IN YOUR PRACTICAL EXAM.  That is there only to help you figure out the circuit.  Draw the diagram given in your lab manual :)

I hope this helps and feel free to give your suggestions and corrections if any :D