The first operational amplifiers (op amps) used what is commonly called split power supplies, meaning the power for the amplifier was symmetrical around ground with both positive and negative polarities. Since most power supplies used transformers to convert 120 V mains electricity, a simple center tapped secondary winding gave easy access to a negative power supply.
Today, many devices now run on battery power, and even mains powered equipment is trending towards having only positive power supplies. But, I don’t recommend ruling out having a negative power supply.
Many signals are still ground referenced and carried on coaxial cables. High performance components, like analog to digital converters, may run on 1.8 V power supplies and require an input signal centered at 0.9 V.
Even the lowest threshold MOS technology cannot generate signals that are truly rail-to-rail and the base-to-emitter voltage (Vbe) on bipolar technologies has not changed significantly from the 0.6 V commonly associated with silicon PN junctions. This means that if an amplifier is going to recreate a signal that swings close to ground, or even more difficult, is ground referenced, a negative power supply is necessary.
Fortunately, generating a negative power supply is very inexpensive, especially if the current requirements are low. A device like the LMR70503 SIMPLE SWITCHER can generate a negative power supply with only 7 external passive components.
The LMH6554 is a differential amplifier designed for both single supply and split supply configurations. Using the LMR70503, an existing 3.3V supply, can be converted to a +3.3 V and -1.7V split supply. With this supply configuration, the LMH6554 output voltage can now swing from -0.6 V to +2.2 V. This range is adequate for driving most analog-to-digital converters and many ground referenced signals such as composite video. Other combinations of supply voltages, like +4 V and -1 V would be ideal for an ADC such as the ADC081500 shown below.
With the advent of switching power supplies there is no reason to limit yourself to only positive power supplies, even when designing battery powered equipment. Don’t be afraid to specify a negative power supply in your next high system design.