This current meter with many scales was found in a 80s American documentation. The operational amplifier is from that time, uncommon nowadays.
This is a well-known RC oscillator configuration using a 741 operational amplifier. The circuit is from...
This circuit is from an old 1967 publication. The circuit uses a programmable unijunction...
The circuit found in a 1983 publication is shown in the figure. Taking advantage of the...