This polarity inverter circuit for voltages down to about -12 V was found in the December 1992 issue of Radio Electronics magazine. The current is a few mA.
April 2017 - Mouser Electronics has the bq25890H integrated circuit consisting of a single 5 A...
This circuit causes an LED to flash at intervals determined by C1 and R2 and for a duration given...
This is a typical common collector amplifier step configuration. The transistor can be used...