This amplified speaker is from a Radio Electronics from September 1988. The power integrated circuit is from that time and the other components are still common today.
This small transmitter with 2 transistors can reach several hundred meters using a 30 to 70 cm...
Built-in Littelfuse itself This SiC N Channel MOSFET for 1200 V can be obtained from Mouser...
This source draws a fixed constant current of 1 mA using a Norton operational amplifier. Other...