Solar charging daytime with 0 V battery output to micro LED chain. At nightfall, solar voltage drops to 0, activating Vout: 3.7 V or alternative Lithium chemistry to power 30 ft (100×) white LED rope lights. Needed current draw around 2 A.

Cell Charging solution (TP4056 or similar) 2B bought on AliExpress or other.

Old question: if I need to manufacture a 5 V- negative voltage, or are there Op-Amps (or other comparators to buy) with GND only? - Already answered.

Follow up question: LM393 or similar can only handle 20 mA. Will I need to involve a power FET, or are there high current load comparators that I somehow missed while googeling?

  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Commented Jun 23 at 16:22
  • \$\begingroup\$ A few U-tube lessons later: \$\endgroup\$
    – Tikun
    Commented Jun 27 at 14:28

2 Answers 2


Single supply op-amps and comparators do exist. You don't need negative voltage.

Just remember that op-amps are poor as comparators just like comparators ar poor as op-amps.


A few U-tube lessons later: The whole design problem I had seems to be simply solved by a logic level depletion mode N type MOSFET: Solar powered Gate, Battery connected to Source + Power/GND, LED chain between Drain and GND. All aided with a few passive components for circuit and component protection.


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