How does a Wilson current mirror work?
A Wilson current mirror is a three-terminal circuit (Fig. 1) that accepts an input current at the input terminal and provides a “mirrored” current source or sink output at the output terminal. It may be used as a Wilson current source by applying a constant bias current to the input branch as in Fig. 2.
What are the advantages of Wilson current source?
The improved Wilson current mirror circuit is made using 4 transistor versions so it is useful for the operation at high currents. The Wilson current mirror circuit provides low impedance at the input. It doesn’t require additional bias voltage and minimum resources are needed to construct it.
Can a PNP mirror be used with a NPN transistor?
Every mirror configuration that can be built with NPN transistors can also be built with PNP transistors, and the general behavior, advantages, and disadvantages of each configuration will be the same. There are only two differences in using PNP rather than NPN transistors in 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.
Why are lateral PNP transistors used instead of vertical?
PNP transistors must be constructed horizontally (known as “lateral PNP transistors”), which means the base region must be wider, so the current gain is necessarily more limited. This does not preclude their use, but it does mean that their lower current gain must be accounted for, and in many cases compensated in some way.
How is the regulation point of a current mirror set?
REVIEW: A current mirror is a transistor circuit that regulates the current through a load resistance, the regulation point is set by a simple resistor adjustment. Transistors in a current mirror circuit must be maintained at the same temperature for precise operation.