Negative rail regulator for analog supplies
The LM7905CT/NOPB is a fixed -5V output linear regulator from Texas Instruments, delivering up to 1.5A continuous current. It is the negative complement to the 7805 positive regulator, commonly used to generate a clean bipolar supply for op-amp circuits, ADC/DAC reference rails, and industrial control boards that need a symmetrical voltage pair. Key ratings include a PSRR of 66dB at 120Hz, which means it attenuates 120Hz full-wave rectifier ripple by a factor of 2000 — enough to keep the negative rail quiet for precision analog loads. The 1.1V maximum dropout at 1A sets the minimum input voltage at -6.1V for a regulated -5V output.
Protection and quiescent current
Built-in over-temperature and short-circuit protection allow the regulator to survive a momentary output short without damage — the die shuts down before the junction exceeds the safe limit. Quiescent current is 1 mA typical, which is the current the regulator consumes internally regardless of load; at light loads this adds to the total supply draw.