The output voltage of a lamp is not a standard term used to describe its operation. Instead, lamps are typically characterized by their power rating (in watts), voltage rating (in volts), and sometimes their luminous flux (in lumens). The voltage rating of a lamp refers to the electrical potential difference that the lamp is designed to operate at, which is usually the voltage supplied by the electrical system it is connected to, such as 120V in North America or 230V in many other parts of the world.

When you connect a lamp to an electrical outlet, the voltage across the lamp will be the same as the supply voltage, assuming the lamp is the only load and there are no significant voltage drops in the wiring. The lamp will then draw a current that depends on its power rating and the supply voltage, according to Ohm's Law and the power equation P = VI, where P is power in watts, V is voltage in volts, and I is current in amperes.

For example, if you have a 60-watt incandescent lamp designed for 120V, it will draw 0.5 amperes of current when connected to a 120V supply (since 60W = 120V * 0.5A). The voltage across the lamp will be 120V, and this is not referred to as the "output voltage" but simply as the operating voltage.

In the case of LED lamps or other types of lamps with built-in drivers or ballasts, the situation can be more complex. These lamps may convert the incoming AC voltage to a different voltage level (often lower) to power the LEDs or other light-emitting elements. However, even in these cases, the term "output voltage" is not typically used to describe the lamp's characteristics. Instead, the focus is on the input voltage requirements and the light output in lumens.

In summary, lamps do not have an "output voltage" in the conventional sense. They have a voltage rating that indicates the supply voltage they are designed to operate at, and they draw current to produce light based on their power rating and the supply voltage.