Free Circuit Diagram

On the circuit diagram, R1 is used to senses current flow of a power supply. We could use JFET as a buffer because Id=Is, therefore the power supply current flow is accurately reflected by the output monitor.

Here’s the circuit diagram:

[Source: National Semiconductor Application Note]

To reach low channel ON resistance (<30 Ohm) and low OFF current leakage, 4-channel commutator uses the 2N4091. The DM7800 voltage translator is a monolithic device. This device give us +10V to -20V gate drive to the JFETs while at the same time giving DTL-TTL logic compatibility.
Here’s the circuit diagram:

[Source: National Semiconductor Application Note]