This circuit is from LinearTechnology Applications of 1997. The circuit uses components of the time used to raise the voltage of a battery from 3 to 6 V.
This circuit was found in Philips documentation from 1967. The phototransistor is from that time,...
We found this third-order Butterworth asymmetric filter in an old manufacturer documentation. The...
We found this circuit in a publication for radio amateurs of 1976. The operational amplifier is a...