Sarjasäädin

Sarjasäädin is a Finnish term that translates to "series regulator" in English. It refers to a type of linear voltage regulator circuit where the control element is placed in series with the load. This control element, often a transistor, acts like a variable resistor, adjusting its resistance to maintain a constant output voltage despite changes in input voltage or load current.

The primary function of a sarjasäädin is to provide a stable and regulated DC voltage from a less stable or fluctuating DC source. It achieves this by dissipating excess voltage as heat. When the input voltage rises or the load current decreases, the sarjasäädin increases its series resistance to drop the extra voltage, keeping the output constant. Conversely, when the input voltage drops or the load current increases, it decreases its resistance to minimize voltage loss.

Commonly implemented using bipolar junction transistors (BJTs) or field-effect transistors (FETs), the sarjasäädin is a fundamental building block in many electronic power supply designs. While simple and effective for moderate power applications, their efficiency can be a drawback, as the dissipated power can lead to significant heat generation, especially when there is a large difference between the input and output voltages. This necessitates the use of heatsinks for higher power dissipation. Despite this, their low noise output and fast transient response make them suitable for applications where power efficiency is less critical than voltage stability and signal integrity.