This circuit was found in an American 1980s documentation. It analyzes the exhaust gas of a vehicle using a special sensor. The indicator is a milliamperimeter.
In the figure we have an interesting protection bridge against power polarity inversion of a...
This amplifier was found in an old publication of 1990. With the changes, it may still be...
Obtained from an English publication, this circuit actually needs a current limiting resistor,...