Iout

Iout, or output current, is the current delivered by an electronic circuit to its load, measured at the output node. It is a key parameter in current sources, amplifiers, and power regulators, and is commonly expressed in amperes (A), milliamperes (mA), or microamperes (µA).

In a current source, Iout is intended to remain constant over a range of load impedances, within the device’s compliance voltage. Real current sources have finite output impedance and a limited compliance voltage, so the actual current can vary if the load demands more or less than the set value, or if the supply voltage changes.

In other devices, such as operational amplifiers and linear regulators, the maximum Iout is limited by the output stage. Exceeding this limit triggers current limiting or protection mechanisms and may distort the output. The term Iout is frequently specified as the maximum deliverable output current.

Applications include constant-current LED drivers, where Iout sets LED brightness; transconductance amplifiers and current-output DACs, which convert voltage to a controlled current; and sensor interfaces where a circuit drives or receives a controlled current from a transducer.

Measurement and control of Iout often involve a sense resistor and feedback to regulate the current, yielding good load and line regulation. In practice, Iout is described with sign conventions, with positive Iout typically defined as current flowing out of the circuit toward the load.

Related terms include Iload (load current), Isense (sense current), and Iin (input current).