We found this simple protection with zener diode in a 1967 Motorola documentation. The zener diode is 18 V, but the components can be changed for operation with other voltages.
April 2017 - The kit for STMicroelectronics STM32F7 32-bit microcontrollers is available from...
This traditional unijunction transistor configuration was found in a 1980s documentation. The functions are...
This different configuration for a crystal galena radio or modernized since a diode is used, has a...