ac vs dc analysis of a BJT

[praneethbobba]

Hi Guys

Can anybody explain the difference between ac and DC analysis of a BJT in detail ??On what basis do we need to carry out ac or dc analysis ? What are the parameters that can be measured in either of the analysis ?

Thanks
Praneeth

 

[chuckey]

Every parameter can be measured with the DC except for things like capacity and Ft. Every AC test should include a statement like " Hfe is 240 at a collector current (DC) of 1mA".
Frank

 

[praneethbobba]

Every parameter can be measured with the DC except for things like capacity and Ft. Every AC test should include a statement like " Hfe is 240 at a collector current (DC) of 1mA".
Frank

Thanks Frank.

Every parameter in the sense , input impedance , output impedances can be measured ??? Also what is meant by Ft. that you mentioned in your reply

Praneeth

 

[chuckey]

Ft is the transition frequency where Hfe goes to 1 (no current gain) :- https://en.wikipedia.org/wiki/Gain–bandwidth_product#Transistors
Frank

 

[LvW]

Thanks Frank.
Every parameter in the sense , input impedance , output impedances can be measured ??? Also what is meant by Ft. that you mentioned in your reply
Praneeth

No - of course, impedances cannot be measured using dc analysis. With dc analyses you can only measure circuit properties for 0 Hz, which means all capacitive effects are not covered.
Thus, only input and output resistances (real part of impedances) can be determined.

 

[praneethbobba]

Thanks Guys for the reply .. Can you suggest any good references or book that I can refer to understand BJT analysis in a wider sense ?

Praneeth

 

[shaswat]

Read boylestad and nashelsky electronic devices and circuits. Its a very good book for both the begineers and the intermediate level people. You can also get the e-book (I have 7th edition but the latest is 10th edition) on the internet.

 

[praneethbobba]

Read boylestad and nashelsky electronic devices and circuits. Its a very good book for both the begineers and the intermediate level people. You can also get the e-book (I have 7th edition but the latest is 10th edition) on the internet.

Thanks Shaswat.