BioAmp EXG Pill Design
Worked for 9 mins 48 sec
Created a project doc
BioAmp Upgrade Design Notes
Upgrade the original single-output BioAmp EXG-Pill into a 2- or 3-output design for simultaneous EOG and EMG acquisition while preserving th...
Schematic topology is in place with three BioAmp channels and matching input/output headers. I’m doing a quick verification now; layout still needs a channel-by-channel PCB placement pass before routing.
Worked for 3 mins 25 sec
Implemented the first-pass 3-output BioAmp Upgrade schematic in Flux: three preserved BioAmp EXG-Pill blocks (
AFE1–AFE3) with matching input/output headers, shared VCC/GND, and separate analog outputs OUT1/OUT2/OUT3. Verification shows no open ERC/component review issues for the current schematic-level implementation, and I recorded the design rationale in BioAmp Upgrade Design Notes.Open items:
- I could not continue into PCB placement/layout because the account currently has no available ACUs.
- The current implementation uses the imported BioAmp block as a preserved channel module; it is not yet expanded into three full TL074/passive-level channels inside Flux.
Suggested next steps:
- Add ACUs, then I can size the PCB, place the three channel blocks/headers, and prepare routing constraints.
- Decide whether you want a module-style 3-channel board using preserved BioAmp blocks, or a fully expanded monolithic TL074/passive PCB.
- After placement, route with analog-input isolation: inputs on one edge, outputs/power on the opposite edge, short symmetric IN+/IN− traces, and solid ground reference.
Fully expanded PCB
Module-style board
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BioAmp Upgrade Design Notes
Goal
Upgrade the original single-output BioAmp EXG-Pill into a 2- or 3-output design for simultaneous EOG and EMG acquisition while preserving the proven original structure.
Source files inspected
BioAmp-EXG-Pill.kicad_schBioAmp-EXG-Pill.kicad_pcbBioAmp-EXG-Pill.libBioAmp-EXG_pill.libBioAmpEXGPill.kicad_mod
Original design architecture observed
The original design is a single-channel BioAmp EXG-Pill block using a TL074-family quad op-amp architecture. The user-facing connectors are:
- Output header J1:
OUT,GND,VCC - Input/electrode header J2:
REF/DRL,IN+,IN-
The internal nets include a first amplifier stage, reference/DRL generation, configurable gain/filter pads, and a band-pass-filtered output. The PCB is a compact 2-layer board with a 1x03 output header on one side and a 1x03 electrode input header on the opposite side.
Upgrade architecture implemented in Flux
I implemented a top-level 3-channel upgrade by importing the original BioAmp EXG-Pill symbol as a reusable preserved analog-front-end block and instantiating it three times:
Table
| Channel | AFE block | Output header | Electrode input header | Output net |
|---|---|---|---|---|
| 1 | AFE1 | J1 | J2 | OUT1 |
| 2 | AFE2 | J3 | J4 | OUT2 |
| 3 | AFE3 | J5 | J6 | OUT3 |
Each channel keeps the same external pin philosophy as the original:
- Output header: pin 1 = OUTx, pin 2 = GND, pin 3 = VCC
- Input header: pin 1 = REFx/DRL, pin 2 = INx+, pin 3 = INx-
VCC and GND are shared across all channels. All signal nets are annotated as analog nets.
Why this is the safest first implementation
Instead of altering the working BioAmp circuit topology, the design duplicates the known-good BioAmp block per channel. This preserves the original gain/filter/reference structure and minimizes risk compared with trying to multiplex one analog chain or share high-impedance EXG inputs between channels.
2-output vs 3-output builds
- Populate AFE1 + AFE2 and headers J1-J4 for a 2-output EOG/EMG build.
- Populate AFE1 + AFE2 + AFE3 and headers J1-J6 for a 3-output build.
Sourcing notes for India
The original TL074/TL074-family quad op-amp is available in the Flux library as TI TL074CPWR / TL074ACDR / TL074IDRE4 options and is typically sourceable via major distributors that ship to India, plus Indian electronics distributors depending on stock. Generic 2.54 mm pin headers are commonly sourceable locally in India.
Important caveats
- The current Flux implementation is a preserved-block top-level schematic, not yet a full transistor/passive-level expansion of all three TL074 channels.
- The imported BioAmp block exposes optional internal filter/gain/2-electrode configuration pins; those are marked no-connect at the top level because the external interface uses OUT/GND/VCC and REF/IN+/IN- only.
- Before fabrication, the PCB layout should be expanded/placed as a compact 3-channel board and the original internal footprints/3D model should be verified or replaced with fully expanded TL074/passive circuitry if a monolithic board is desired.
Recommended next layout direction
Use a repeated channel layout: three identical BioAmp lanes, with inputs grouped on one board edge and outputs/power on the opposite edge. Keep each channel's high-impedance IN+/IN- traces short, symmetric, and separated from the other channels; use a continuous ground reference and avoid routing output/power traces near electrode inputs.
Goal
Source files inspected
Original design architecture observed
Upgrade architecture implemented in Flux
Why this is the safest first implementation
2-output vs 3-output builds
Sourcing notes for India
Important caveats
Recommended next layout direction
