Datasheet

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3 Components
4 Board Layout
5 Measurement Tips
Components
Components that have RF performance similar to the ones listed in Table 1 may be substituted. C
1
and C
2
need a larger voltage rating for ± 15V dual supplies.
Table 1. Component Descriptions
PART DESCRIPTION
C
1
, C
2
Tantalum Chip Capacitor, SMD EIA Size 3528, 20V
C
3
– C
8C
Multilayer Ceramic Chip Capacitor, SMD 1206, 50V
J
1A
– J
3C
SMA or SMB Board Jack (Amphenol 901-144-8)
EMI-Suppression Ferrite Chip, SMD 1206
L
1
, L
2
(Steward LI 1206 B 900 R)
Terminal Block, 3.5mm Centers
P
1
(On-Shore Technology ED555/3DS)
R
1A
– R
8C
Metal Film Chip Resistor, SMD 1206, 1/8W
R
1
and R
7
set the I/O impedance, R
2
through R
6
set the gain, and C
1
through C
7
are supply bypass
capacitors. C
3
is optional; it adds a bypass between the supplies that improves distortion performance for
some models. L
1
and L
2
are ferrite chips that can reduce interactions with the power supply at high
frequencies. If not desired, they can be replaced with 0 Ω resistors. R
8
through R
13
and C
6
and C
7
are
optional components that support op amps with special functions.
For single-supply operation, do not connect L
2
; otherwise, the –V
S
input to P
1
would be at ground
potential.
This demonstration fixture is a two-layer PCB. (See Figure 3 .) It uses a ground plane on the bottom, and
signal and power traces on the top. The ground plane has been opened up around op amp pins 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.
The location and type of capacitors used for power-supply bypassing are crucial to high-frequency
amplifiers. The tantalum capacitors, C
1
and C
2
, do not need to be as close to pins 7 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.
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 ( ≤ 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 Ω resistor on the probe tip to isolate its capacitance from the circuit.
SBOU006A – November 1999 – Revised June 2006 DEM-OPA-SSOP-3A Demonstration Fixture 3
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