This simple logic test circuit with 3 LEDs was found in October 1985 Radio Electronics magazine. The power supply is according to the logic, and this version is indicated for TTL.
The output voltage of this circuit is proportional to the square root of the input voltage....
This circuit uses a common diode as sensor. The output goes from 0 to 10 V with the temperature change in...
These days the unijunction transistor (UJT) is not common, but IF you have one you can mount this...