Self-oscillating H bridge lights white LED from one cell

摘要

You can build a self-oscillating H bridge by replacing the pull-up collector resistors of a classical BJT (bipolar-junction-transistor) astable multivibrator with PNP BJTs (Figure 1). Because this circuit oscillates at supply voltages as low as 0.6V, you can use it in general low-voltage, low-power push-pull applications. You can, for example, drive a diode-capacitor charge pump to generate negative supply voltage in battery-powered systems. This Design Idea shows how to use it to light a white LED from one cell without an inductor.