This circuit, for vehicles with a 6 V battery, was found in the 1964 RCA transistors manual. Transistor 2N3054 can be replaced by a TIP41.
This passive tuned circuit was found in a 90s Popular Electronics. The coils must be according to the...
This circuit is suggested by Motorola and is based on the well-known 723, integrated voltage...
This circuit appears in other versions in this same section of the website and in other sections with...