This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
This circuit was found in a Popular Electronics of the 90s. The resistor R4 determines the load...
Obtained from a 1980s Signetics documentation, this circuit uses a common integrated circuit at the...
We found this circuit in the Linear Applications Handbook by National Semiconductor. The circuit is...