Solving BJT Circuits Example

In this video, I explain how to solve BJT circuits, and why we like to use the approximation of Vbe,on = 0.7V (or 0.5V, or 0.6V). I solve a simple BJT circuit assuming infinite current gain using the Vbe = const approximations and more exactly using the exponential dependence on voltage, and show that the error in making these guesses in typical situations is quite low.

Hope you found this video helpful, please post in the comments below anything I can do to improve future videos, or suggestions you have for future videos.

[JordanEdmundsEECS]

Note for the enlightened: this video assumes the BJT is operating in forward active (for the unenlightened, I will discuss what that means in a future video).

[martinsimbona]

Your vidz are soo resourceful, thanks for the time you take to make them. Keep up man

[stefano.a]

For supposing Vbe, the problem occurs when BJT is biased to have a very low Ic, so that it is in the limits of active zone. In that case whe would use che exponential version but: where we can find the “Is” in the datasheet of the component? For example, for a 2N3904 where is it? (there are only the cut off currents that if you insert in the formula it leaves to wrong results). In that case there is also the problem for the formula Ib = Is exp (Vbe/Vt) that for low currents is not valid for silicon diodes. The formula becomes Ib = Is exp (Vbe/(eta x Vt)) where eta ia a coefficient between 1 and 2 where 1 is for an ideal diode

[yewedmund]

Will more videos be added to this playlist? This Electronics II playlist has much fewer videos than Electronics I: Semiconductor Physics and Devices

[hirdeshkumar]

which book are you using for this course ?