Mini MOSBius
A playground for analog microelectronics on TTSKY25a and all future Sky shuttles.
Matt Venn
•1 June 2026
Circuit layout render of the Mini MOSBius
MOSBius is a fantastic, practical tool for learning the fundamentals of analog microelectronics. Simulation is one thing, getting hands on with mosfets and a scope is something else!
Inspired by Peter Kinget’s MOSBius project last year, we commissioned Andrew Kang to create a smaller version for Tiny Tapeout - Mini MOSBius!
It’s like an FPGA, but for learning analog electronics. Instead of lookup tables we have the basic building blocks of analog circuits: transistors, current mirrors, differential pairs and an opamp.
In this post I’ll explain how it works by creating and testing 2 circuits: an inverter and an SR latch.
Adjustable Inverters
Let’s start with one of the simplest and well known 2 transistor building blocks, the humble inverter. We can use Sylvain Munaut’s configurator to make the connections and get the bitstream.
Mini MOSBius Configurator UI
The red dots are showing where the transmission gates are active, creating nodes in the circuit. The 2 dots in the center
are connecting the split buses so that I can use ua[4] as an input and ua[5] as an output.
Inverter schematic
Injecting a 1kHz input (green) and we get our inverted (in blue) signal output.
Oscilloscope output showcasing inverter behaviour
Zooming in we can see that the inverter has about a 50ns rise time. Let’s see if we can steepen it by using a wider mosfet.
~50ns rise time for this configuration
Setting the width to 4 in the configurator we get around 25ns. An easy experiment that drives home both that P mosfets are weaker than N mosfets, and one way to compensate is by increasing their width.
~25ns rise time with a wider mosfet
Latching Data
The next circuit is an SR latch. This uses 6 of the 8 mosfets to build 2 inverters to store the data and 2 pull down switches for set and reset.
SR latch schematic
If the point 4 is high, then point 1 is driven low by the right inverter, which reinforces the blue point high through the left inverter.
Here we see it in operation, with data in blue, set in yellow and reset in green.
set and reset
Available on future Sky shuttles!
It’s been great to get hands on and verify Mini MOSBius. We just had a great group call with the Zero to ASIC course - participants were able to discuss a circuit and try modifications on the fly.
But the most exciting part is that Mini MOSbius is now included on all our future Tiny Tapeout Sky130 based chips, so along with your own design you’ll get a fully featured analog playground to tinker with!
Last modified by Kristaps Jurkans on 16 June 2026. Commit 139c611. Suggestions?