# Pn junction

## Homework Statement

I came across a question asking " which one of these circuits has the largest resistance to the current?

## The Attempt at a Solution

* In A the positive terminal of the battery is connected to the p-type region and the negative one to the n-type region (forward bias) so, the field due to the battery is opposite to the internal field in the transition region and therefore, it weakens it. The resistence will be small and the current will flow.
* C is the opposite case of A since it shows that the pn diode is connected in reverse direction. The resistance will be large and the current is almost zero.
But I'm not sure about the B case.

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ehild
Homework Helper

## Homework Statement

I came across a question asking " which one of these circuits has the largest resistance to the current?
View attachment 227031

## The Attempt at a Solution

* In A the positive terminal of the battery is connected to the p-type region and the negative one to the n-type region (forward bias) so, the field due to the battery is opposite to the internal field in the transition region and therefore, it weakens it. The resistence will be small and the current will flow.
* C is the opposite case of A since it shows that the pn diode is connected in reverse direction. The resistance will be large and the current is almost zero.
But I'm not sure about the B case.
B is a "resistor " with positive charge carriers. It can be a piece of p-type semiconductor.

cnh1995
Homework Helper
Gold Member

## Homework Statement

I came across a question asking " which one of these circuits has the largest resistance to the current?
View attachment 227031

## The Attempt at a Solution

* In A the positive terminal of the battery is connected to the p-type region and the negative one to the n-type region (forward bias) so, the field due to the battery is opposite to the internal field in the transition region and therefore, it weakens it. The resistence will be small and the current will flow.
* C is the opposite case of A since it shows that the pn diode is connected in reverse direction. The resistance will be large and the current is almost zero.
But I'm not sure about the B case.
You are right in your analysis. The diode in figure C is reverse-biased and will offer the largest resistance to the current (assuming that the applied voltage is low enough to prevent reverse-breakdown).
Figure B shows a p-type semiconductor. Its conductivity will depend on the amount of doping and temperature.

Eman 55