This power stage with two transistors was found in Radio Electronics magazine from October 1963. The transistors must be equipped with heatsinks and the supply voltage is 12 V.
This circuit was found in a 1992 PE Hobbyst. The circuit detects the presence of spy...
This configuration is suggested by Mullard (Philips) in an old manual of 555 integrated circuits....
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...