AD605
Rev. F | Page 18 of 24
EVALUATION BOARD
The AD605-EVALZ provides a platform for the circuit designer
to become familiar with the many operating and performance
features of the AD605 variable gain amplifier. It is a factory-
designed, surface-mount assembly fully tested and ready for
service. Figure 42 is a photograph of the AD605-EVALZ. Multiple
inputs, test points, and jumpers provide circuit configurations that
support any of the operating options of the device. Figure 43 is a
schematic of the board.
Power is required from only a single 5 V supply capable of
supplying 55 mA to 60 mA quiescent current.
00541-043
Figure 42. AD605–EVALZ Evaluation Board
INPUT CONNECTIONS
The AD605 VGA accepts differential or single-ended input
signals and provides single-ended outputs. The SMA connectors
enable either configuration to be used, as well as the output and
gain control signals. Each of the I/O ports is also available at a
test-loop labeled for easy identification.
The input resistance at each of the four input SMA connectors is
50 , consisting of the 175 Ω, ±40 Ω resistance of the attenuator
ladder network in parallel with the external 69.8 Ω resistors. For
single-ended operation, unused inputs can be left disconnected
or optional jumpers installed. Either VGA input is usable; for
noninverting operation, the INPx is used, and for signal inversion,
the INMx is used.
ADJUSTING GAIN, COMMON-MODE, AND
REFERENCE LEVELS
The gain of each channel is adjusted with trimmers, GN1ADJ and
GN2ADJ. Trimmer VREF ADJ adjusts the gain scaling in dB/V (or
gain slope), and VOCM ADJ adjusts the output common-mode
voltage for both channels. For dynamic gain control, JP1 and
JP4 can be removed and the signal applied at the SMA
connectors, GN1 and GN2.
OUTPUT CONNECTIONS
SMA connectors, OUT1 and OUT2, are the output connectors.
Series resistors and capacitors are included for termination and
dc blocking purposes. The output of the AD605 has a common-
mode value of one-half the supply (unless amended by a voltage
applied to the VCM pin).
Table 4 lists jumpers and their functions, and Figure 44 shows
the evaluation board in a typical test configuration.
Table 4. Table of Jumpers
Jumper Function Default Configuration
JP1 Connects trimmer GN1ADJ to pin VGN1. This jumper can be removed for an ac signal at VGN1. Installed
JP2 Grounds the IN1 pin via C2. User supplied
JP3 Grounds the IN2 pin via C5. User supplied
JP4 Connects trimmer GN2ADJ to Pin VGN2. This jumper can be removed for an ac signal at VGN2. Installed
JP5 Connects trimmer VOCMADJ to the VOCM pin. This jumper can be removed for the half supply default VOCM. Installed
JP6 Shifts the gain of Channel 2 up or down by 14 dB. Installed
JP7 Shifts the gain of Channel 1 up or down by 14 dB. Installed
JP8 Connects trimmer VREFADJ to the VREF pin to change the gain slope. Installed
