Datasheet

50W
1kW
OPA695
V
OUT
1kW
OPA820
0.1 Fm
1N4150
V
REF
+V
IN
R
G+
R
G-
-V
IN
FB
V
G
200W
50W
50W
50W
100W
V
IN
50W
950W
VCA820
Out
VCA820
SBOS395C –OCTOBER 2007–REVISED OCTOBER 2009............................................................................................................................................ www.ti.com
AGC LOOP The demonstration fixtures can be requested at the
Texas Instruments web site (www.ti.com) through the
In the typical AGC loop shown in Figure 83, the
VCA820 product folder.
OPA695 follows the VCA820 to provide 40dB of
overall gain. The output of the OPA695 is rectified
MACROMODELS AND APPLICATIONS
and integrated by an OPA820 to control the gain of
SUPPORT
the VCA820. When the output level exceeds the
reference voltage (V
REF
), the integrator ramps down
Computer simulation of circuit performance using
reducing the gain of the AGC loop. Conversely, if the
SPICE is often useful when analyzing the
output is too small, the integrator ramps up increasing
performance of analog circuits and systems. This
the net gain and the output voltage.
principle is particularly true for video and RF amplifier
circuits where parasitic capacitance and inductance
DESIGN-IN TOOLS can play a major role in circuit performance. A SPICE
model for the VCA820 is available through the TI web
page. The applications group is also available for
DEMONSTRATION BOARDS
design assistance. The models available from TI
predict typical small-signal ac performance, transient
Two printed circuit boards (PCBs) are available to
steps, dc performance, and noise under a wide
assist in the initial evaluation of circuit performance
variety of operating conditions. The models include
using the VCA820 in its two package options. Both of
the noise terms found in the electrical specifications
these are offered free of charge as unpopulated
of the relevant product data sheet.
PCBs, delivered with a user's guide. The summary
information for these fixtures is shown in Table 1.
Table 1. EVM Ordering Information
LITERATURE
BOARD PART REQUEST
PRODUCT PACKAGE NUMBER NUMBER
VCA820ID SO-14 DEM-VCA-SO-1B SBOU050
VCA820IDGS MSOP-10 DEM-VCA-MSOP-1A SBOU051
Figure 83. AGC Loop
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Product Folder Link(s): VCA820