The film reminded me of how we amateurs work together exchanging ideas and helping each other with all sorts of issues – antennas, radios, projects – etc. So it has been with this LDMOS amplifier project for me. (Silicon-based LDMOS FETs are widely used in RF power amplifiers for base-stations where requirements for high output power with a corresponding drain to source high breakdown voltage ratings are required – typically cabable of very high frequencies.) Exchanging ideas with many of my ham friends for this project has been the key for its success. After two failures with LDMOS chips it was pointed out to me that the source to drain voltage ratings of the devices being tested was not high enough to take the 55VDC analog power supply being used. As a rule of thumb the rating should be divided by a factor of “2”, and that would mark the upper limit. The original unit we used had a rating of 100 volts so anything over 50 volts was likely to result in a “failure”. The NXP BLF 188XR has a rating of 135 volts…high enough to use a 50VDC source…..
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