We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
We found this circuit in an American publication from the 1990s. Any FET can be used. The circuit...
This circuit can be used as an optical switch or photosensor to excite TTL logic. The transistor can be...
This sensitive circuit was found in a Texas Instruments optoelectronics manual. The transistors can be...