ZN414

ZN414 in TO92 package

The ZN414 was a low cost, single-chip AM radio integrated circuit. Launched in 1972, the part was designed and supplied by Ferranti, but was also available from GEC-Plessey. The ZN414 was popular amongst hobbyists as a fully working AM radio could be made with just a few external components, a crystal earpiece and a 1.5 V cell.

The original ZN414 chip from Ferranti was supplied in a 3-pin, metal TO-18 'transistor' package whereas the GEC part and later Ferranti ones (ZN414Z) used the plastic TO-92 encapsulation. Later variants, the ZN415 and ZN416, came in 8-pin DIL packages and included a built-in amplifier that could drive headphones and small speakers directly.

The radio circuit inside the ZN414 was based on a design known as Tuned Radio Frequency (TRF). The TRF design is much simpler than the popular, but more complex, superheterodyne radio circuit often used in modern AM receivers. It was principally the use of the TRF circuit that allowed almost a whole radio to be fitted into one small, three pin package.

ZN414 in basic functional circuit

The manufacturing process for the ZN414 chip used a relatively new (for the time) technique known as Collector Diffusion Isolation (CDI). CDI was invented by engineers at Bell Telephone Laboratories and subsequently developed into a commercial process by Ferranti in the UK.[1]

The original ZN41x family have not been manufactured for some time, but modern equivalents to the original 3-pin ZN414 are available, with part codes of MK484, TA7642 and (mainly in India, the Far East & Australasia) YS414 and LMF501T. Note that on the YS414 part, pins 1 (output) and 3 (ground/earth) are transposed.

ZN414 pinouts

Notes

  1. ↑ Technology Transfer and the British Microelectronics Industry, 1950-75: John F WILSON
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