I do not see a compelling reason to use 2N5109 for new designs, it is an obsolete part. Central and Microchip terminated the production. The last direct equivalent, the NTE278 is discontinued since last year. New 2N5109 are chinese substitutes, some of them are of decent quality, some are not.
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For temperature compensation it may make sense to use a Diode to bias a transistor. Avoid Zener/avalanche diodes, they generate noise. LEDs may make sense, if you can double use it as power indicator.
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regards
Fred
