The purpose of this circuit is only to increase the input resistance of a multimeter, since there is no voltage gain. The batteries are 9 V and operational equivalents can be used.
This circuit was found in an Experimenters Handbook of the 1990s. The purpose of this circuit is to...
This source, from a 1982 documentation, uses a triac to control the power and voltage applied to...
This circuit was found in the September 1984 issue of Radio Electronics magazine. The circuit has...