Intermediate-frequency amplifier

Intermediate-frequency (IF) amplifiers are amplifier stages used to raise signal levels in radio and television receivers, at frequencies intermediate to the higher radio-frequency (RF) signal from the antenna and the lower (baseband) audio or video frequency that the receiver is recovering.

This allows most of the gain in the form of a fixed-frequency amplifier, simplifying tuning.

Compare to its predecessor, the tuned RF receiver.

IF amplifiers might use double-tuned amplifiers or staggered tuning to generate the appropriate frequency response needed.

Media related to IF amplifiers at Wikimedia Commons

The IF stage from a Motorola 19K1 television set circa 1949.
Discrete transistor 455 kHz IF amplifier.
More modern IF amplifier and demodulator in integrated circuit form