SOT-223 LBA – Linear Buffer Amplifier

The SOT-223 LBA is a compact, wideband class AB RF buffer module designed for experimentation, prototyping, and educational use. It leverages inexpensive, readily available SOT-223 transistors (e.g., 2N2222 and its complement) to provide a hands-on platform for exploring transistor behavior, gate/base drive characteristics, and linear amplification in the HF band.

Features

• Class AB linear buffer using two SOT-223 transistors

• Wide bandwidth: ~1–20 MHz with simple components

• Output power: ~1.5 W typical

• Optional input matching network: tunable series capacitor + shunt inductor for HF optimization

• SMA edge-mount connectors for easy input/output interfacing

• Support for 4W 50 Ω dummy load for convenient power measurements and scope monitoring

• Versatile experimentation: suitable for:

  • Small QRSS or QRSP transmitter setups

  • Antenna and matching experiments

  • RF transistor characterization

  • Educational lab exercises

Design Goals

• Hands-on learning: Observe real transistor behavior and switching speed

• Prototyping flexibility: Leave pads open or populate optional components to experiment with different matching networks

• Open-source friendly: All design files, schematics, and layout are intended for community experimentation and adaptation

Typical Applications

• HF linear amplification testing

• RF input matching exploration

• Small signal QRSS transmitter experiments

• VNA-based measurements and tuning exercises

The SOT-223 LBA is ideal for hobbyists, educators, and RF enthusiasts who want a compact, low-cost, and flexible platform for understanding transistor linearity and HF signal behavior.