Can a PNP transistor be used in a mirror circuit?
All of the current mirror circuits presented in previous pages in this group have used NPN transistors. This is by no means necessary; as shown to the left, we can easily use PNP transistors to build current mirrors.
How are mirror magnitudes related to PNP current?
Another way to provide different current magnitudes at different mirror outputs is to change the areas of the transistor emitters. A larger emitter area will transmit more current for a given value of V BE. Another way to link NPN and PNP current mirrors is shown to the right.
What’s the difference between PNP and NPN transistors?
There are only two differences in using PNP rather than NPN transistors in current mirrors. The first is the obvious fact that the applied voltage polarity must be reversed. The emitters are connected to +V, while the collectors are referenced to a more negative voltage. This can be ground as shown here, or any voltage more negative than +V.
How is the current mirror of a sink replicated?
current mirror replicates the input current of a current sink or current source as an output current. The output current may be identical to the input current or can be a scaled version of it.
What are the output characteristics of a PNP transistor?
The Output Characteristics Curves for a PNP transistor look very similar to those for an equivalent NPN transistor except that they are rotated by 180o to take account of the reverse polarity voltages and currents, (that is for a PNP transistor, electron current flows out of the base and collector towards the battery).
Is it possible to make NPN and PNP transistors on the same die?
The second factor to be considered is that in an IC, while it is always possible to manufacture both NPN and PNP transistors on the same die, it is not possible to make them the same way or to match their parameters. NPN transistors are made vertically, so the width of the base region can be closely controlled to enable high values of current gain.