I work with max. 18 V, hobby. Don´t want to mess around with AC. Which integrated circuits to buy to learn/ experiment with: -comparator -opamp -voltage regulators -voltage stabilizers -optocopler -CMOS -TTL -A-D, D-A converters -microprocessors -temperature sensors -timer -quartz crystal I am learning what these are. It would be good to know which fall in that range and approximately what specifications to buy.