I have a LM471 op-amp and a single DC 5V source. Is it possible to double the source voltage using this op-amp? Can the op-amp be powered by the very signal to be amplified? I tried simulating such situation in Multisim and it seems power/signal have to be from different sources. Why is that?
A segment on my 7 segment display requires voltage higher than 5V. I want to boost my 5V power (double it, for example) and use the boosted voltage to lit the display. I don't want to use a separate power source just to power the op-amp. I understand the out current will be lower, but it doesn't matter in my situation.
Of course different elements might be necessary in this circuit, but I don't want to use things like 555 timers, just analog parts.
Answer
If you have a microcontroller (as I suspect) driving your display, you could probably use a spare pin with pwm to drive a simple capacitive voltage doubler. Thus you'd need only common parts (caps, diode, a bjt/mosfet) - no need for 555, opamp or whatever and no inductor so little added noise.
Edit : here is the classic voltage doubler circuit :
simulate this circuit – Schematic created using CircuitLab
C1 should be much smaller than C2 (lower C1 gives lower ripple, but lower curtent capacity and slower voltage ramp-up), and critically diodes should have lowest possible Vf. You won't get exactly doubling from this circuit as it is, but for what I guess your application is that may not matter much.
Drive PWM pin by setting it to 127, and choose frequency matching C1 (or C1 matching the PWM frequency).
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