Comments on: How NPN transistor works? Tutorials of forward & reverse biasing of an NPN transistor

By: Chinmay Joshi

Chinmay Joshi — Wed, 04 Mar 2026 15:14:12 +0000

In reply to kitle. Very nice article. Thanks for it.

By: Prof. Dr. Dattaraj Vidyasagar

Prof. Dr. Dattaraj Vidyasagar — Thu, 26 Jun 2025 05:48:54 +0000

Srinidhi https://vsa.edu.in/how-npn-transistor-works-understanding-forward-reverse-biasing-of-an-npn-transistor/#Concept_of_Transistor_Biasing

By: Srinidhi

Srinidhi — Wed, 25 Jun 2025 03:41:51 +0000

One small correction required, for RR Biasing collector must be positive wrt Base here

By: Yash Vidyasagar

Yash Vidyasagar — Sat, 10 Nov 2012 09:31:22 +0000

In reply to ankush. Since the current through the transistor is controllable, it means that the internal resistance of the transistor is changing. The fact that when its base-emitter resistance changes it reflects the change in its collector-emitter resistance. Hence it is termed as transfer of resistance-transistor.

By: ankush

ankush — Fri, 09 Nov 2012 18:35:42 +0000

is transistor simply means transfer of resistors? how can u say so?

By: Yash Vidyasagar

Yash Vidyasagar — Tue, 06 Nov 2012 02:32:24 +0000

In reply to ashwini. Inverter is defined as the circuit that converts DC voltage source into AC voltage at required frequency. Now CMOS-FET inverter is a device which is actually a FET (Field Effect Transistor) in CMOS technology. CMOS-FET inverter is a simply a push-pull type FET circuit as shown below, which amplifies both halves of the AC cycle and give you reliable output of AC source.

By: ashwini

ashwini — Mon, 05 Nov 2012 18:05:13 +0000

In reply to Yash Vidyasagar. thank you for your immediate response. sir I would like to know working of CMOSFET inverter.

By: Yash Vidyasagar

Yash Vidyasagar — Thu, 01 Nov 2012 13:03:43 +0000

In reply to ashwini. It is always the case, that when voltage across base-emitter junction of NPN transistor is greater than or equal to 0.7V, then it is forward biased. When this voltage is quite large, say around 3V or more (upto certain limit), then total the number of free electrons in emitter layer start participating in conduction of electric current through the transistor. This condition is called as saturation of transistor and in this condition we can use it just like a switch which is ON. And when the base voltage is quickly reduced to zero, this process of conducting current suddenly stops and we can use the transistor just like a switch which is OFF...! What type of CMOS info you need?

By: ashwini

ashwini — Thu, 01 Nov 2012 06:59:53 +0000

sir, I have doubt when npn transistor is on or off i.e is it right if the voltage at the base is more than the emiter volage applied the transistor is on. I would also like to know when does the transistor act as switch as well as CMOS working.

By: Yash Vidyasagar

Yash Vidyasagar — Sat, 20 Oct 2012 09:20:35 +0000

In reply to radhika rao. You may also refer other articles on configurations of transistor, to clear your doubts.

By: Yash Vidyasagar

Yash Vidyasagar — Sat, 20 Oct 2012 09:17:45 +0000

radhika rao http://vsagar.com/2012/10/20/simple-details-common-collector-configuration-npn-transistor-2/

By: radhika rao

radhika rao — Fri, 19 Oct 2012 17:08:55 +0000

i have a doubt regarding forward bias and reverse bias connection for cc amplifier. can u plz help me out

By: Yash Vidyasagar

Yash Vidyasagar — Fri, 21 Sep 2012 11:52:24 +0000

In reply to ANJAN. My dear friend,

The BE junction is forward biased. So the physical barrier within it is more easy to surmount for electrons coming from emitter layer.
Once then enter base layer, they have strong mutual repulsion among them.
So some of them have the tendancy to get attracted towards the +ve terminal of Vbe.
Hence base current (conventional current) flows INTO base, rather than coming out...!
But don't consider the -ve terminal of Vcb battery, since it is NOT CONNECTED to BE junction, it is connected to CB junction.
So you are not allowed to consider the ELECTRICAL CONNECTIVITY of Vcb with this process.

Please also read the explanation given on your next comment.

I like the way, you are asking the queries. It increases the wisdom of understanding this process in deep.

By: Yash Vidyasagar

Yash Vidyasagar — Fri, 21 Sep 2012 11:42:54 +0000

In reply to ANJAN. The reason that the Vcb >> Vbe, is as follows....

The CB junction is reverse biased.
So it has large physical gap than BE junction, as this junction is forward biased.
When electrons come from emitter layer into base layer, they are crowded in small area of base.
So they acquire sufficient repulsive force among them to go into collector layer.
But this force is still slightly less than the required force to overcome CB junction barrier.
So a strong attractive force from collector side is required to pull these electrons towards collector layer and then towards +ve terminal of battery.
Hence the Vcb >> Vbe.

By: ANJAN

ANJAN — Thu, 20 Sep 2012 16:47:52 +0000

In the base junction negative terminal of Vcb and positive terminal of Vbe is connected. Vcb grater then Vbe . So electrons should flow towards base . So current should flow out of the base. ( opposite to diagram ) Then why current is flowing towards base ? Please explain ......... I don't understand this basic concept .....

By: ANJAN

ANJAN — Thu, 20 Sep 2012 16:32:21 +0000

Why base collector voltage >> base emiter voltage ?????

By: ANJAN

ANJAN — Thu, 20 Sep 2012 06:57:54 +0000

In reply to Yash Vidyasagar. THANKS.......

By: ANJAN

ANJAN — Thu, 20 Sep 2012 06:55:13 +0000

By: Yash Vidyasagar

Yash Vidyasagar — Sat, 08 Sep 2012 12:40:07 +0000

In reply to chien. The electrons repel each other due to mutual repulsion...like charges, as they have...

By: chien

chien — Thu, 06 Sep 2012 13:20:21 +0000

really confusing for someone who has no background from fwd bias-> f) Now large number of electrons in emitter layer is repelled by negative terminal of Vbe and they flow towards b-e junction. why are the electrons in emitter layer is repelled when it's connected to negative junction of the battery which is also full of electrons??