Mr.Raghuram,

By your wording, "I could not get the curves", I would suggest you to check the following.

i) Are you operating the device in the active region around the DC quiescent point.

ii) Are your meters chosen with the correct ratings( Micro/Milli)

~KS

Dear Srikanth (KS),

Yes, the meters are of proper ranges. (Base current - micro and collector current - milli).

The following are specs of the circuit:

BC 107 Transistor (npn BJT)

Base current limiting resistor - 10K

Collector current limiting resistor - 100 ohms

I also tried varying the resistor values, still I could not get the desired output.

Raghu

Dear mr. Raghuram,

Do you hold the VCE constant durign taking the Input characteristics? As for the output characteristics, try to produce some base current and keep it constant when change VCE.

Best regards,

Toncho Papanchev

Hello Raghuram,

I am attaching some files or images that depict the characteristics curves of the BJTs.

1) From your Problem 1, please keep it in mind, that although the BE junction behaves as transistor, it is not a regular diode!!!  What I mean to say that as the transistors have very high current gain, the diode of BE junction will require very small current of the order of few tens of micro-amps as against the few milli amps.

Therefore my recommendation is that you try the input characteristics with smaller values of currents.

2) Frr Problem 2, as Toncho has stated above, check if there is a little base current flowing through the BE junction in order to make the transistor conducting. Without a base current the transistor would be in cut-off state and you shall not observer current flowing through the collector of the device.

I hope you shall be able to sort out the problems.

Best luck!

There are some confusing statements in your account:

'The base current keeps on increasing (even before the base emitter voltage reached 0.7V, base emitter current flows) - typical diode curve behaviour is not seen'

The current does not abruptly turn on at '0.7V'.  The base current follows an exponential relationship with VBE. You will see this if you plot the current on a log scale.

I suggest you show us your measuring circuit set-up.

(Note that the curves posted by Prasanna look odd and not what I would expect for a BJT.)

Dear all,

Please find the attached circuit which I tried.

Dear Steve,

In input chara, the base current didn't flow abruptly. But the exponential behaviour was not obtained. Also in the output chara, there was no collector current thought there was base current and the transistor was working fine (tested BJT). Please find the set up in the image attached above. Kindly advise.

Raghu

Hello Raghuram,

"1) Input Chara - The base current keeps on increasing (even before the base emitter voltage reached 0.7V, base emitter current flows) - typical diode curve behaviour is not seen"

Yes, this is what we are expecting. Base current starts flowing even before VBE reaching 0.7V.

"Output Chara - The collector current is not flowing in the circuit (with increase in the collector voltage)"

possibly, the problem is with biasing. Transistor may be at cutoff state.

Above all, make sure that you are following a proper circuit arrangement.

Hope this helps.

Thank you Rohith. I am using the circuit diagram as attached above. Is that correct?

The Ronith's answer is correct and detailed. I would like to draw attention that these are static characteristics.

1) Input characteristics - Ib=f(Ube) when Ucs=const

2) Output characteristics - Ic=f(Uce) when Ib=const

The circuit diagram is correct, but it is important to hold Uce constant during changing Ube and measuring Ib for each one curve for input char, and to hold Ib constant when change Uce and measure Ic for each one curve for output char. Hope to be useful.

Hello Raghuram,

With regards to your problem No 1 i.e.  Input Chara - The base current keeps on increasing (even before the base emitter voltage reached 0.7V, base emitter current flows) - typical diode curve behaviour is not seen.

I feel that you might be facing this problem due to Early effect i.e. base width modulation since if you probably was increasing the collector voltage ( reverse bias) which leads to decreasing the effective base width and hence making a better diode which conducts heavily even before .7 V is reached.

In such case the collector current should start flowing which you said is not happening.

Raguram,

Yes. Circuit is ok.

Sorry for delay.

Rohith