Laser FPGA Hat

Project Owner

Name: Alek Platform: Alchitry Au V2 FPGA

Project Overview

This project is a custom hat board for the Alchitry Au V2 that interfaces a laser transmitter and a high-speed optical receive path with the FPGA.

The board is intended to handle laser control, convert small high-speed detector current pulses into usable voltage signals, and provide a clean digital output to the FPGA for further processing.

What I Hope to Learn

• High-speed analog and mixed-signal PCB design
• Laser diode driving and optical signal detection
• High-speed comparator and amplifier design
• FPGA interfacing and digital signal processing

Current Design

The design currently includes:

• Alchitry Au V2 hat-board interface
• Laser diode drive circuitry
• High-speed transimpedance / amplifier stage
• Input biasing to keep the analog front end within its valid operating range
• High-speed comparator stage for converting the received pulse into a digital FPGA signal

The analog front end is currently being simulated in LTspice. A bias of approximately 0.4 V has produced the best pulse response so far with limited ringing. The next step is to integrate and test the comparator stage before moving into the PCB layout.

Major Components

Component	Purpose
Alchitry Au V2	FPGA processing and control
Laser diode	Optical transmitter
High-speed op-amp / TIA	Converts detector current pulses to voltage
High-speed comparator	Converts analog pulses to FPGA logic
Custom PCB	Au V2 hat and analog interface

Current Milestones

Milestone	Status
Initial circuit architecture	Complete
Analog front-end simulation	In Progress
Comparator integration	Next
Hat schematic and pinout	In Progress
PCB layout	Not Started
Hardware testing	Not Started

Project Files

This repository will contain:

• KiCad schematic and PCB files
• LTspice simulations
• FPGA source code
• Datasheets
• Test results and documentation

Project Image