How to build a current mirror circuit using discrete transistors?
When building a real current mirror circuit using discrete transistors, the two transistors should be epoxy-glued together (back-to-back) so that they remain at approximately the same temperature. To illustrate this dependence on equal temperature, try grasping one transistor between your fingers to heat it up.
How does q 2 in a mirror circuit work?
With a constant base current and a nearly constant β ratio, Q 2 will drop as much or as little collector-emitter voltage as necessary to hold its collector (load) current constant. Thus, the current mirror circuit acts to regulate current at a value set by the potentiometer, without regard to load resistance.
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.
Can a pair of NPN transistors build a current mirror?
Larger “power” transistors may not exhibit the same behavior at these low current levels. However, any pair of identical NPN transistors may be used to build a current mirror. Beware that not all transistors share the same terminal designations, or pinouts, even if they share the same physical appearance.
Can a bipolar junction transistor be used as a current mirror?
Bipolar junction transistors are widely used for current mirroring. The first trick to use bipolar junction transistor as a current mirror circuit is to construct an exponential voltage to current converter using the transistor.
How is the current mirror circuit simulated in Proteus?
The current mirror circuit is simulated using Proteus models. In the left side, the current mirror circuit using 2N2222 BJT is shown where two identical transistor pair is used. Instead of the programming resistor, a potentiometer is used to control the current flow in the live simulation. This same thing is created for the 2N6660 MOSFETs.