DC Voltage Regulator

Description: A voltage regulator is an electronic circuit that provides a stable DC voltage independent of the load current, temperature and input DC voltage variations. It has a very wide application range and it can be used to control the speed of a motor, the brightness of a LED or lamp, etc. Practically, it can be used in any application that uses a regulated DC supply. Procedure: We can implement a simple series voltage regulator that is using a transistor and Zener diode. The load current is passing through the series transistor Q1 & that’s the reason why we call the circuit a series voltage regulator . You can see that we feed the unregulated DC supply through the input terminals so that we can get the regulated across the load. Here, the zener diode is providing the reference voltage. Observation: The base voltage of transistor Q1 is held to a relatively constant voltage across the Zener diode. For example, if 8V zener (i.e., VZ = 8V) is used, the base voltage of Q1 will remain approximately 8V. Hence , Vout = VZ – VBE. Case 1 : Output Voltage Decreases Under this circumstance , the increased base-emitter voltage will cause transistor Q1 to conduct more, thus increasing the output voltage. Hence, the output voltage will be maintained at a constant level. Case 2 : Output Voltage Increases Under this circumstance , the decreased base-emitter voltage will cause Q1 to conduct less, thus reducing the output voltage. Hence, the output voltage will be maintained at a constant level. Conclusion: The changes in zener current are reduced by a factor ß. Hence, the effect of zener impedance is tremendously reduced and we get a more stabilised output. Despite the fact that changes in zener current are reduced to a considerable extent, the output is not absolutely constant. This happens because both VBE and VZ decrease with the increase in room temperature. It is not easy to change the output voltage as no such means is provided.