I've been shopping for a voltage regulator that works in a range of .5-1.5 (+/-.5) Volts, but they are not easily found.
I'm wondering if anyone knows whether they even exist, or possibly how to make one.
Thank you,
L.
Electronic – *very* Low voltage regulator
voltage-regulator
Related Solutions
You can use an external pass transistor with a fixed 7805 regulator, see for example page 14 of National Semiconductor's datasheet.
It's also possible to use the LM317 to build tracking regulators that can be connected together so that they share the power.
But the reason the integrated packages don't go much above 1A is the dissipation due to the product of the difference between input and output voltages times the current. Switching regulators are much better for higher currents than linears because of this thermal problem.
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.
The above image was from the Fairchild 7805 datasheet that may be found here:
Best Answer
The problem is that your 500mV output requirement is rare, so that very few regulators use a reference that is lower than ~1.25V (a few use 800mV).
One way to get this to work is to amplify the feedback signal using an op-amp. A gain of 3 would allow you to use any regulator with a reference voltage up to 1.5V.
Edit:
Say your regulator has a 1.25V reference, so you'd normally use a voltage divider RA/RB on the output such that Vout = 1.25V (1+ \$\frac {R_A}{R_B})\$.
Add a suitable op-amp to amplify the output voltage:
Vin comes from your output voltage. Say it is 500mV and your regulator has a reference voltage of 1.25V. Vout goes to the feedback input of the regulator (where the tap on the voltage divider goes).
In general your output voltage will be Vout = Vref (\$\frac {R_G}{R_F+R_G})\$, so in this particular example we might pick Rg = 10K and thence calculate Rf = 15K.