Using JFETs, this circuit from a 90’s American documentation can generate signals of 0.15 Hz. The JFET can be of any general-purpose type like the BF245 or MPF102.
Found in a 90s Electronic Design, this circuit employs CMOS functions to mix signals from two...
This frequency band below 15 kHz converter was found in a Popular Electronics from the 90's. The...
This is one of the channels of an amplifier suggested by Westinghouse in 1970s documentation. The circuit...