This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
This circuit, which can be used on an optical link, is suggested by the Texas Instruments...
This source, from a 1998 publication, can be used as a battery charger. The diodes are for 10 A x...
We found this circuit in an old publication on oscilloscopes. Its purpose is to observe the Ie /...