Texas Instruments OPA3695EVM Evaluation Module OPA3695EVM OPA3695EVM Datenbogen
Produktcode
OPA3695EVM
1/3
OPA3695
+5V
DIS
50W
V
O
R
F
R
G
R
M
+
6.8 F
m
0.1 F
m
50
Load
W
-5V
+
6.8 F
m
0.1 F
m
50
Source
W
V
I
1/3
OPA3695
+5V
+V
S
DIS
V /2
S
604W
100W
V
O
V
I
604W
R
G
49.9W
R
F
348W
0.1 F
m
0.1 F
m
+
6.8 F
m
0.1 F
m
50
Source
W
60.4W
SINGLE-SUPPLY OPERATION
SBOS355A – APRIL 2008 – REVISED SEPTEMBER 2008
...............................................................................................................................................
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simple resistive divider from the +5V supply (two
604
604
Ω resistors). The input signal is then ac-coupled
into this midpoint voltage bias. The input voltage can
swing to within 1.6V of either supply pin, giving a
1.8V
swing to within 1.6V of either supply pin, giving a
1.8V
PP
input signal range centered between the
supply pins. The input impedance matching resistor
(60.4
(60.4
Ω) used for testing is adjusted to give a 50Ω
input match when the parallel combination of the
biasing divider network is included. The gain resistor
(R
biasing divider network is included. The gain resistor
(R
G
) is ac-coupled, giving the circuit a dc gain of
+1V/V, which puts the input dc bias voltage (2.5V) on
the output as well. Again, on a single +5V supply, the
output voltage can swing to within 1V of either supply
pin
the output as well. Again, on a single +5V supply, the
output voltage can swing to within 1V of either supply
pin
while
delivering
±90mA
output
current.
A
demanding 100
Ω load to a midpoint bias is used in
this characterization circuit. The new output stage
used in the OPA3695 can deliver large bipolar output
used in the OPA3695 can deliver large bipolar output
Figure 36. DC-Coupled, Inverting, Bipolar-Supply,
current into this midpoint load with minimal crossover
Specification and Test Circuit
distortion,
as
illustrated
by
the
+5V
supply,
third-harmonic distortion plots.
Notice that in this configuration (shown in
),
the noninverting input is tied directly to ground.
Because the internal design for the OPA3695 is
current-feedback, trying to achieve improved dc
accuracy by including a resistor on the noninverting
input to ground is ineffective. Using a direct short to
ground on the noninverting input reduces both the
contribution of the dc bias current and the noise
current to the output error. While the external R
Because the internal design for the OPA3695 is
current-feedback, trying to achieve improved dc
accuracy by including a resistor on the noninverting
input to ground is ineffective. Using a direct short to
ground on the noninverting input reduces both the
contribution of the dc bias current and the noise
current to the output error. While the external R
M
is
used here to match with the 50
Ω source from the test
equipment, the input impedance in this configuration
is limited to the R
is limited to the R
G
resistor. Removing R
M
does not
strongly impact the dc operating point because the
short on the noninverting input of
short on the noninverting input of
provides
the dc operating voltage. This application of the
OPA3695 provides a very broadband, high-output
signal inverter.
OPA3695 provides a very broadband, high-output
signal inverter.
Figure 37. AC-Coupled, G = +8V/V, Single-Supply
Specification and Test Circuit
The OPA3695 may be used over a single-supply
range of +3.5V to +12V. Though not a rail-to-rail
range of +3.5V to +12V. Though not a rail-to-rail
While
the
circuit
of
shows
+5V
output design, the OPA3695 requires minimal input
single-supply operation, this same circuit may be
and output voltage headroom compared to other
used for single supplies that range as high as +12V
very-wideband
video
buffer
amplifiers.
The
key
nominal. The noninverting input bias resistors are
requirement of broadband single-supply operation is
relatively low in
to minimize output dc offset
to maintain input and output signal swings within the
as a result of noninverting input bias current. At
useable voltage ranges at both the input and the
higher signal-supply voltages, these resistors should
output.
be increased in order to limit the added supply
current drawn through this path.
current drawn through this path.
The circuit of
shows the single-supply
ac-coupled, gain of +8V/V, video buffer circuit used
as the basis for the
as the basis for the
table
and
curves. The circuit of
establishes an input midpoint bias using a
14
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