The operational amplifier of this circuit can be the 741. The circuit has very low consumption and can be powered by two 9-B batteries. Low voltage amplifiers can be used.
This circuit works as a useful field meter for radio amateurs. We found it in documentation from...
The circuits below were found in amarican publication of the year 1958. The transistors are...
This circuit was found in a 1975 documentation. Current general-purpose transistors can be used,...