You have to be more specific; d/c, a/c, frequency, power in, power out, power supply, efficiency, etc.
One example could be a CRT video driver. They are usually found on the board on the neck on CRT's, and amplify 1V dc (to 5-25MHz) up to around 90V. They usually require a PSU around 110-130V dc and operate at a power level around 1-2W.