ZN414
The ZN414 is a low cost, single-chip AM radio integrated circuit. Launched in 1972, the part was designed and supplied by Ferranti, but was second sourced 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 cel
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 used the plastic TO-92 encapsulation. Later variants, the ZN415 and ZN416, came in 8-pin Dual [in-line package|DIL packages] and included a built-in amplifier that could drive headphones and small speakers directly.
The radio circuit inside the ZN414 is based on a design known as Tuned [radio frequency receiver|Tuned Radio Frequency]. The TRF design is much simpler than the popular, but more complex, superheterodyne radio circuit often used in modern AM receivers. It is principally the use of the TRF circuit that allows almost a whole radio to be fitted into one small, three pin package.
[Image:Zn414-basic-circuit.png|thumb|center|upright=3|ZN414 in basic functional circuit]
The manufacturing process for the ZN414 chip used a relatively new technique known as Collector Diffusion Isolation. CDI was invented by engineers at Bell Telephone Laboratories and subsequently developed into a commercial process by Ferranti in the UK.
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 YS414 and LMF501T. Note that on the YS414 part, pins 1 and 3 are transposed. Currently only the TA7642 is manufactured and is used in some AM/FM radios that use the 70 kHz IF single chip VHF-FM IC.
[Image:ZN414 Pinout.png|thumb|center|upright=1.5|ZN414 pinouts]