Voltage to Frequency Converter 2 (CB9448E)

Found in an EDN from the 90s, this circuit uses operational amplifiers from that time, which are uncommon nowadays.

| Clique na imagem para ampliar |

IR tone remote control (CB20972E)
This circuit is from a Popular Electronics from the 90s. The circuit has a tone frequency...
Door buzzer or alarm (CB20492E)
This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose...
Electronic die (CB21712E)
This circuit is based on a common cathode 7-segment display. The circuit is based on CMOS...