A Termination Insensitive Amplifier for Bidirectional Transceivers

W7ZOI Design

• Paper - A Termination Insensitive Amplifier for Bidirectional Transceivers - W7ZOI (Wes Hayward) design
• Transistor Models and the Feedback Amplifier
• Termination Insensitive - input impedance that does not depend upon the output load
• Bi-directional - amplifiers in both directions
• 50 ohms in/out
• BNC or SMA Connectors
• Transformer-less
• Power applied to one half at a time - determines signal flow direction
• ~30 mA per side

W7ZOI Schematic

* Use

• Between RF/LO mixer (IF output/input) and crystal filter
• Between Crystal Filter and Product Detector / Balanced Modulator

Schematic in KiCAD

• Single channel
• With SPICE directives

• Both channels
• With SPICE directives

NGSPICE Simulation

• NGSPICE run from KiCAD
  • Tutorial: ngspice simulation in KiCad/Eeschema
• +24 dB @12V
• 2N3904 Alternate Node Sequence (MMBT3903 - SOT23)
  • KiCAD order 1 2 3 is the SPICE normal order
  • NGSPICE order: 3 1 2

• Closely matches

• Across Band

CAD

SMT Build

Assembly Sheet

• W7ZOI TIA Assembly Sheet - Rev 1