FET Bias Board Design
This is a simple bias board design using the ICL7660 dc-dc converter IC, designed to support 2 gaasfets. A suitable power supply was needed for use with the surplus LNA boards that are sold by www.rfmicrowave.it. It's designed to run from 7 to 24 volts and provide an adjustable negative supply as well as a 'select on test' positive supply current.
The component values for the bias board are as follows:
- C1 - Electrolytic 10uF 25v
- R1 - 150 or 200 ohm (150 ohm)
- R2 - 4.7 to 10K (10k)
- VR1 - 5 to 20K (10k)
- REG - 78l05 (5 volt)
- DC-DC - ICL7660 8pin DIL
The diode is for reverse polarity protection, a 1N4001 or similar is fine. 78L05 and ICL7660 are obtainable from Maplin electronics in the UK. The artwork is available here - its 300dpi and will result in a print that is 5.3 cm X 1.8 cm
