This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This traditional symmetric power supply configuration with the 7812 and 7912 regulators was found...
Thes astable was found in old publication of 1968. The circuit uses general purpose germanium...
This circuit uses a common diode as sensor. The output goes from 0 to 10 V with the temperature change in...