Electronics - Bipolar Junction Transistors (BJT) - Discussion


Three different Q points are shown on a dc load line. The upper Q point represents the:

[A]. minimum current gain
[B]. intermediate current gain
[C]. maximum current gain
[D]. cutoff point

Answer: Option C


No answer description available for this question.

Shahrukh said: (Mar 31, 2011)  
Why it is said that maximum current?

Sakshi said: (Jun 11, 2011)  
While ploting dc load line current is on x-axis & volt on y-asis...so upper most pt will represent max current...

Shubhadeep said: (Jul 31, 2011)  
q-pt represents the present condition of device (transistor).

When q-pt is upper the voltage drop across it is very small, so.

The current is max.

Sapna said: (Aug 3, 2011)  
@Shubhadeep is right due to less voltage drop current is max.

Varsa said: (Jan 2, 2012)  
As the upper Q point represents high output current it means high current gain.

Satya said: (Apr 1, 2012)  
As the X-axis is for current & y-axish for voltage.So answer must be max current gain.

Rahman said: (Apr 2, 2012)  
In DC load line on x axis is cutoff and why axis is saturation point.

Ramesh Reddy said: (May 23, 2012)  
DC load line is plot of Ic versus Vce it indicates as point is upper it has max current and viceversa.

Puneet Panwar said: (Jul 23, 2012)  
Current gain will be maximum as for low voltage change we will get high change in the current values, hence slope will be more or we can say current gain will be high.

Kalpana said: (Sep 29, 2012)  
In DC loadline voltage is taken on X-axis & current is taken on Y-axis. Hence the upper Qpoint will consists maximum current.

Bikram said: (Dec 24, 2012)  
There are three region on Q-point, the lower one is cut-off, midle one is active and the upper most region is saturation and also y-axis represents current n x-voltage. So saturation n current axis means max. Current.

Sravani said: (Jul 21, 2013)  
x-axis of transfer characteristics of transistor is VCE and y-axis is IC so peak or highest point on the why axis is the point of maximum collector current or output current. So this the point of maximum current gain (ic/ib) in case of ce mode.

Vishal said: (Aug 28, 2013)  
As I is leading voltage Upper q-pt be max current.

Rajamohan said: (Nov 23, 2013)  
Q-Point is drawn by a linear line from Ic to Vce so as q point is moving up it is moving towards High Current and Low voltage so the current is maximum.

Akshay said: (Dec 15, 2013)  
-> Current gain = B(beta) = Ic/Ib.

-> Upper Q-Point denotes higher Ic.
-> Thus for const. Ib.
-> B(beta) Must be high.

Anubhav Chaturvedi said: (Jan 9, 2014)  
There is a very simple reason - plotting dc load line you see that y axis is for output current while x axis is for output voltage. According to given condition upper Q point implies maximum output voltage, hence maximum gain.

J Ramya said: (Nov 24, 2015)  
Upper part means saturation region. In saturation region output junction is also forward biased. So maximum current flows that's the why current gain is high.

Kona Lakshman said: (Nov 1, 2016)  
Is Dc characteristics of BJT for NPN and PNP is same? Anyone please explain.

Sindhu said: (Jun 16, 2020)  
It's minimum current gain!

Because when a transistor is biased in the saturation mode, Ic<(beta x Ib).

This condition is very often used to prove that a transistor is biased in saturation mode.

Reference: Electronics Circuits Analysis and design by Donald A Neaman (Third Edition)

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