We found this circuit in the February 1983 issue of Radio Electronics magazine. The 4-digit circuit is based on dedicated integrated circuits of the time. The power supply is not shown.
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...