Optocouplers are available in many different configurations. The most common type is the transistor output optocoupler. Transistor optocouplers can be optimized for different CTRs, different input currents and different output currents. These items can also meet different safety standards that are required around the world. The most common configurations for transistor output optocouplers are the DC input, AC input and Darlington output. High-speed optocouplers have been growing in usage. Any application requiring isolation of data rates greater than 1 Mb/sec are considered high speed. Optocouplers are commonly available at 1 Mb/sec with either digital or analog outputs. 10 Mb/sec, and 15 Mb/sec digital output optocouplers are also available. Higher speeds can be attained as well. High-function optocouplers have built-in integrated circuits allowing them to perform special tasks. MOSFET / IGBT optocouplers are used to isolate low power control circuits from high power MOSFET / IGBT drivers. Another high-function optocoupler is the isolation amplifier optocoupler. Used primarily in the feedback circuit of a motor control circuit, these devices are available with both digital and analog outputs.