Plug-in semiconductor substitute for pentode - has FET input element plus output transistor mounted on valve foot for direct substitution

摘要

The semiconductor unit is mounted on a valve base (14), which can be plugged in as a substitute for a pentode valve. The circuit uses an FET as input element, connected as a source-follower to the base of an output transistor connected in common emitter circuit. An adjustable resistance may be included between the base and emitter of the output transistor to control the ratio of output current and output voltage, and a second adjustable resistance to control the ratio of the input voltage and output current.