This circuit is from a 1965 Motorola documentation. The transistors are of the time as is the uninformed magnetic sensor.
This circuit produces a signal in the range corresponding the the VHH channels between 2 and 6....
This circuit is from a 70s documentation. The maximum sampling rate is 800 Hz. The operational...
Any JFET can be used in this circuit suggested by Electronics Now magazine, April 1993. The...