Texas Instruments DEM-OPA-SO-2A Demonstration Fixture DEM-OPA-SO-2A DEM-OPA-SO-2A Datenbogen
Produktcode
DEM-OPA-SO-2A
OUTB
J2B
J2B
INB
J1B
J1B
OUTA
J2A
INA
J1A
+VS GND VS
-
GLUE AREA
DEM-OPA-SO-2A
REV. B
(MAY 2010)
P1
R7A
R5A
R4A
R2A
R7A
R2B
R38
R4B
R5B
R6A
R1A
R18
C3
-VS GND +VS
R3A
C2
L2
L1
C4
C1
R6B
C5
U1
Pin 1
R7B
OUTB
INB
OUTA
INA
(a) Component Side Silkscreen and Metal
(b) Ground Plane Side Silkscreen and Metal (bottom view)
Board Layout
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4
Board Layout
This demonstration fixture is a two-layer PCB. (See
.) It uses both a ground plane and power
traces on the inner layers. The ground plane has been opened up around op amp pins that are sensitive
to capacitive loading. Power-supply traces are laid out to keep current loop areas to a minimum. The SMA
(or SMB) connectors may be mounted either vertically or horizontally onto the board edge. The location
and type of capacitors used for power-supply bypassing are crucial for high-frequency amplifiers. The
tantalum capacitors, C
to capacitive loading. Power-supply traces are laid out to keep current loop areas to a minimum. The SMA
(or SMB) connectors may be mounted either vertically or horizontally onto the board edge. The location
and type of capacitors used for power-supply bypassing are crucial for high-frequency amplifiers. The
tantalum capacitors, C
1
and C
2
, do not need to be close to pins 8 and 4 on the PCB and may be shared
with other amplifiers. See the individual op amp data sheet for more information on proper board layout
techniques and component selection.
techniques and component selection.
(1)
The board name shown in the silkscreen for an earlier version of the fixture is DEM-OPA268xU with the
Burr-Brown Revision A design finalized in May 1998.
Burr-Brown Revision A design finalized in May 1998.
Figure 3. DEM-OPA-SO-2A Demonstration Board Layout
5
Measurement Tips
This demonstration fixture, with the component values shown, is designed to operate in a 50
Ω
environment; most data sheet plots are obtained under these conditions. It is easy to change the
component values for different input and output impedance levels. However, do not use high-impedance
probes; they represent a heavy capacitive load to the op amp, and will alter the amplifier response.
Instead, use low-impedance (
component values for different input and output impedance levels. However, do not use high-impedance
probes; they represent a heavy capacitive load to the op amp, and will alter the amplifier response.
Instead, use low-impedance (
≤
500
Ω
) probes with adequate bandwidth. The probe input capacitance and
resistance set an upper limit on the measurement bandwidth. If a high-impedance probe must be used,
place a 100
place a 100
Ω
resistor on the probe tip to isolate its capacitance from the circuit.
4
DEM-OPA-SO-2A Demonstration Fixture
SBOU003B – May 1998 – Revised May 2010
Copyright © 1998–2010, Texas Instruments Incorporated