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 1970 General Electric circuit is an equivalent configuration to the previous one with PNP...
This circuit was obtained in a Texas Instruments 2012 documentation, which consists of a current...
We obtained this circuit in a Maxim documentation from the 90s. The circuit is based on the...