The log stages are simply undegenerated diff pairs, as shown in Fig. A4, which are not
hard-limiting. This smooths the cusps of the transfer curve sketched in Fig. A2. The
"summing amp" is simply two resistors.
The L-17C architecture is similar to that of Fig. A4, with an extra input amp to provide
more gain, and a buffer between the log stages and the output amplifier (which was also
added for drive power).
(1)
For an excellent reference, with specific orientation to radar and EW, see Hughes,
Richard Smith. Logarithmic Amplification. Artech House, Dedham, MA, 1986. Mr.
Hughes developed, more than twenty years ago, the general circuit approach
which is now widely used.
-A4-
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