We found this circuit in a Philips documentation from 1965. The circuit uses a common LDR sensor and the transistors are general purpose types. TR2 can be a BD135.
This circuit uses an operational amplifier that is uncommon today, but it can be implemented with...
This circuit was obtained from a 1978 Practical Wireless. It generates a low frequency, low...
This filter was found in an old publication from 1977. The circuit must use a simple two-voltage source...