We found this circuit in the November 1992 Radio Electronics magazine. The circuit uses an LDR as a sensor and the transistor can be any general-purpose transistor.
Found in Linear Technology documentation from the 90s, this circuit uses an operational amplifier...
This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...
The figure shows the basic circuit of a relaxation oscillator with operational amplifier. The...