5 GHz VCO with ÷8 divider (Tiny Tapeout SKY26d)

An FM transmitter on a Tiny Tapeout 2x2 analog tile (SKY130). An NMOS LC VCO running at around 5 GHz feeds a CML divide-by-8, so the output is in the 600–700 MHz range. Feeding audio (e.g. a guitar) into vcont makes FM that you can receive with an SDR.

Layout

Block diagram

Pins

Pin	Function
ua[0]	RF output (+), around 600–700 MHz
ua[1]	RF output (−)
ua[2]	vcont, VCO tuning input (around 0.4 V)

Notes

• The output frequency depends on vcont, supply voltage, process and temperature.
• The VCO is sensitive to supply noise, so a clean LDO is recommended.

Documentation

How it works and how to test it: docs/info.md

About Tiny Tapeout

Tiny Tapeout is an educational project that makes it easier and cheaper to get designs manufactured on a real chip.