Category:Current mirrors

Current mirrors are used extensively for the biasing of analog integrated circuits or also as part of current DACs. Their function is to replicate (or mirror) the current from the main current source branch into any other branch. The mirrored current is often scaled by integer ratios (by transistor sizing) to the desired bias value for that particular branch. Current mirrors are especially well suited to integrated circuits, due to the fine control over device matching properties available in integrated circuits (as opposed to that possible in discrete or hybrid implementations).

Much like for current sources, the ideal mirror must present an infinite output resistance to it's load, meaning it should maintain the desired current output regardless of fluctuations in output voltage. The output resistance and the minimum required voltage across the mirror -- otherwise known as the compliance voltage -- are two of the most important performance metrics for current mirrors.

The degree to which a current mirror topology can attain the largest output resistance and lower compliance voltage while considering complexity, area and power consumption largely determines it's performance in practice.