This circuit, which can be used as a shield, was found in American documentation from the 1970s. This configuration appears elsewhere in this section from other sources.
This circuit was found in a 90s Hands-on Electronics. The transistor can be a BC548. What it does...
In the figure we show how to use an LM324 as a voltage comparator the reference voltage is...
This circuit is based on an LM3900 transconductance operational amplifier, found in 1992...