This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
This circuit was found in an EDN from the 90s. For the components indicated, the frequency is 10 kHz....
This circuit provides voltages and a 1 kHz signal for measurement bridges. The circuit is from...
We found this circuit in an old documentation, but it is still current. General purpose...