PC36-1D Rev. 5
September 12, 1990
APPLICATION NOTES FOR THE ANADYNE, INC. L-17C *M*
LOGARITHMIC VIDEO AMPLIFIER
1.
INTRODUCTION
ANADYNE's purpose in designing this IC was to develop a DC-coupled LVA which would greatly
facilitate the production of detector log video amplifiers (DLVAs) which easily meet or exceed
present program performance specifications. Particular attention was paid to the incorporation of
features which enable rapid and inexpensive assembly and tuning in a production environment. In
addition, we wished to anticipate likely future requirements by achieving greatly-decreased power
usage, substantial size reduction, greatly improved long-term reliability, and significantly lower
noise than existing DLVAs.
Both the linearity and the gain and drift stability of the L-17C are excellent (within ±0.3 and
0.5 dB
respectively) over the full military temperature range, as is its performance at very high duty-cycle.
A recovery time of 200 ns (to within
1 dB) has been readily achieved at the high-power end of a
45-dB dynamic range, using simple recovery nets. Recovery is faster at lower powers. Quiescent
power is about 450 mW at
6 volts. Rise times of less than 10 nanoseconds are practical in
appropriate layouts, with a transit time of <20 ns. The amplifier is very quiet, with a typical TSS of
less than -46.5 dBm at 10 MHz video bandwidth, including the noise contribution of the tunnel
diode detector (K = 700). The rms noise figure of the L-17C itself is about 1.5 nV/Hz
1/2
at 25
o
C.
The body size of the standard 36-pin IC package is about 10mm x 10mm.
These application notes were prepared principally for new users of the L-17C. In general, they
refer primarily to the normal 36-pin package configuration of the IC, as used in the ANADYNE-
designed test and evaluation PC board (designated the PC36-1). The purpose of this PC board is
to expedite the process of hands-on familiarization with the L-17C's performance characteristics
and versatility. This experience will also facilitate the subsequent design of miniaturized PC
boards using chip components, or the design of hybrid structures for the user's specific
applications. The general internal architecture and functional pinout of the IC is presented in Fig.
1(a), and the normal package pinout diagram is shown in Fig. 1(b).
The L-17C was designed for a wide variety of applications. As a consequence, the ancillary
circuitry for the PC36-1 test board may appear complex at first sight, with a relatively large number
of components labeled as "FS" (factory select). However, it will never be necessary to use all
these components in any given application. Many, in fact, are intended to produce competing
effects, such as "speedup" or "slowdown" of one or another of the amplifiers internal to the IC.
Furthermore, once the optimum external circuitry for a given application and layout has been
specified, almost all the components can be preselected for subsequent units of the same type.
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