This step of two transistors has a high input impedance due to the use of FET. We can use BF245 for this function and the bipolar can be BC548. The circuit is from an 1975 American documentation.
The MOS field effect transistors of this circuit are not very common, as it is a project from the...
If interference occurs in several receivers, much more interesting than placing a filter on each...
This single-cell Li-Ion battery charger was found in a 2005 Linear Technology manual. The circuit...