This step of two transistors has a high input impedance due to the use of FET. We can use BF245 for this function and the bipolar can be BC548. The circuit is from an 1975 American documentation.
Found in American documentation from the 1990s, this circuit receives modulated infrared signals. The...
The figure shows a simple test circuit for optical isolators with photodiodes. The circuit was...
The purpose of this heat detector is to find hot spots on a board or other locations. The sensor is...