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.
The circuit shown in the figure is the version activated at the low level, of the previous circuit...
This circuit is from an old American documentation using LEDs in the rectification. The circuit...
This circuit consists of an emitter follower, presenting unit voltage gain implemented with an...