Circuit VR: Current Mirrors
Last time we looked at Spice models of a current sink. We didn’t look at some of the problems involved with a simple sink, and for many practical applications, they are perfectly adequate. However, you’ll often see more devices used to improve the characteristics of the current sink or source. In particular, a common design is a current mirror which copies a current from one device to another. Usually, the device that sets the current is in a configuration that makes it very stable while the other device handles the load current.
For example, some transistor parameters vary based on …read more