For measurements between 30 and 40º C this circuit was found in the documentation of 1968. The sensor is a difficult component to obtain today.
The cut-off frequency of the filter shown in the figure can be adjusted to values between...
This circuit was found in a Popular Electronics from the 90s. The components used are all common...
This circuit uses a dual floodgate MOSFET not very easy to obtain today. Its handling is very...