This circuit was found in RCA documentation from the 1980s. The circuit uses LDRs of the time and the 50 uA instrument has zero in the center. R1 and R2 may have 2k2 and R3 10k typically.
Using L144 operational, this circuit applies to other equivalent operational. The circuit is from...
This circuit has a gain of 34 dB and a good power to be used as an audio booster in cars. The...
The circuit shown in the figure can be implemented with more modern equivalent operating systems. We...