OPA3695_14 Datasheet, PDF (23/39 Pages) Texas Instruments – Triple, Ultra-Wideband, Current-Feedback OPERATIONAL AMPLIFIER with Disable

OPA3695
www.ti.com ............................................................................................................................................... SBOS355A – APRIL 2008 – REVISED SEPTEMBER 2008
EVALUATION MODULE
To evaluate the OPA3695, an evaluation module
(EVM) is available. This EVM allows for testing the
OPA3695 in many different systems. Inputs and
outputs include SMA connectors commonly found in
high-frequency systems along with 50Ω characteristic
impedance traces. Because the traces are very short,
changing the input and output terminations resistors
from 49.9Ω to 75Ω has essentially no impact when
evaluating video signals. Several unpopulated
component pads are found on the EVM to allow for
different input and output configurations as dictated
by the user.
By default, all channels of the EVM are configured for
a noninverting gain of +2V/V. If inverting configuration
or differential input configuration is desired, then
simply replacing R1, R4, and R7 with desired
resistors allows these configurations to be set up
quite easily. Also, the feedback and gain resistors
can be easily replaced to allow for any gain desired.
Note that even though the default gain of the
OPA3695 is +2V/V, or 6dB, the output 49.9Ω source
termination resistors (R13, R14, and R15) and the
user-applied 50Ω end-termination resistance
commonly found in test systems makes the overall
system gain appear as 0dB.
Each channel's disable control is independently
configured. By default, the use of jumpers JP1, JP2,
and JP3 allows for a quick and easy method to
evaluate the disable function of the OPA3695.
However, if this control must be externally controlled,
then using the SMA connectors J10, J11, and J12 is
recommended. The termination resistors R19, R20,
and R21 should to be changed to match the source
impedance, but it is not required. Attention to the
voltage appearing at each disable pin is required to
ensure proper operation of this feature. The voltage
at the disable pin is shown in the Electrical
Characteristics section of this data sheet.
This EVM is designed to be primarily used with split
supplies from ±2.5V up to ±6V. This EVM can be
used with a 5V single-supply up to 12V, but care
must be taken to account for the input termination
resistor connections to ground. Adiitionally, the 100uF
bypass capcitors C1 and C2 are rate at 10V. If single
supply is used with more than 10V applied, these
capacitors should be changed to accomodate the
increased supply voltage. The OPA3695 allowable
input range is defined in the Electrical Characteristics
section of this datasheet and must be adhered to for
proper operation. Also note that the gain setting
resistors are also connected to ground. Thus, any dc
offset is increased proportionally by the gain. As
such, using the EVM as a split supply is
recommended even if the final use is single-supply.
Example: if the final usage is to be 12V single-supply,
then using ±6V supplies simplifies the dc reference
voltage to mid-rail—or an equivalent 6V for a
single-supply configuration.
Figure 46 shows the OPA3695EVM schematic.
Figure 47 to Figure 50 illustrate the four layers of the
EVM PCB, incorporating standard high-speed layout
practices. Table 3 lists the Bill of Materials for the
EVM as supplied from Texas Instruments.
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): OPA3695
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