Monday, 31 October 2016

Increasing output voltage of a fixed linear regulator


I'm using a AMS1117 fixed 3.3V linear regulator and I want to increase its output voltage to about 4V. The input voltage to the 1117 is in the range of 9-10V.


Wikipedia suggests that it's possible to put a zener or resistor on the ground terminal of the regulator to change its output voltage but it provides no citation or reference. Anyone know how this works?



Answer



Fairchild datasheets for their LM78XX series of linear regulators contain a circuit for increasing the output using a resistor to hold the reference above ground. I guess how well it works in practice will depend on how stable the quiescent current is over the operating range for the AMS1117.


enter image description here



The above image was from the Fairchild 7805 datasheet that may be found here:


http://www.fairchildsemi.com/ds/LM/LM7805.pdf


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