Intermediate-frequency amplifier

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The IF stage from a Motorola 19K1 television set circa 1949. 19K1 IF stages.jpg
The IF stage from a Motorola 19K1 television set circa 1949.
Discrete transistor 455 kHz IF amplifier. IF amplifier 455 kHz.jpg
Discrete transistor 455 kHz IF amplifier.
More modern IF amplifier and demodulator in integrated circuit form Profitronic VCR7501VPS - controller board - Philips TDA8341-93705.jpg
More modern IF amplifier and demodulator in integrated circuit form

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. [1]

Contents

Uses

IF amplifiers in heterodyne receivers apply gain in a frequency band between the input radio frequency and output audio frequency or video frequency, often following one stage of RF amplifier. 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. Some use more than one IF frequency.

Commonly used circuits

References

  1. Walker, H. R. (2005). "Intermediate-Frequency Amplifiers". Encyclopedia of RF and Microwave Engineering. doi:10.1002/0471654507.eme187. ISBN   978-0471654506.
  2. Sandel, B. "Intermediate Frequency Amplifiers" (PDF). frank.yueksel.org/. Archived from the original (PDF) on December 2, 2013. Retrieved September 12, 2025.
  3. "The Art of Alignment". www.vintage-radio.net. Retrieved 27 January 2019.

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