When an amplifier stage has two or more transistors, it is best to have all devices of the same gain and output to better equalize power sharing and d.c. current in each device. Other companies only offer matching of "Beta Codes" — hardly what matching is really about.
RF Parts Company has developed a testing program to provide the service technician with Premium Matched RF Power Transistors, having the best quality and performance. First, we select transistors with the same "Lot Number" and "d.c. Beta". (This is where others stop and call the transistors matched.) Next, we test each transistor's B-E, B-C, and C-E junctions with a curve tracer to separate out those with "undesirable" juncion characteristics. Only transistors with low Collector-Base leakage (Icbo) are accepted for further testing. Finally, these "Premium" selected parts are placed in our RF Test Fixture, one at a time. The test measurement is noted on each part. Our transistor Power Gain test is measured at about 50-60% of maximum peak power rating. (Note: different drive power levels are used for the various transistors, and test numbers only apply for the particular part number under test.)
We select the best parts for matched sets of 2, 4, 8, 16, etc. The number on the outside of the envelope is the Power Measurement of each transistor as discussed above. Use of our selected parts will help assure top performance and reliability in multi-transistor power amplifiers.
Examples of popular transistors selected for these tests are: MRF150, MRF422, MRF448, MRF454, MRF455, MRF492, SRF3662, SRF3749, SRF3775, 2SC2290, 2SC2879, 2SC2904, 2SC3133, SD1407, SD1446, SD1460, etc.
