Second order active voice filter (CB7568E)

This filter for the 300 Hz to 3 kHz range was found in an American documentation from the 90's. The operational amplifier is a double 741.

| Clique na imagem para ampliar |

Telephone Monitor (CB12655E)
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
FET Transconductance Meter (CB3932E)
This interesting FET-tester circuit was obtained from an old American documentation. The bipolar...
TV Booster (CB23771E)
This old VHF TV booster that also serves FM was found in Radio Electronics magazine from April...