Datasheet

1/2
OPA2690
+5V
+
DIS
-5V
50 LoadW
50W
175W
50W
50 SourceW
402W
402W
+
6.8 Fm
0.1 Fm 6.8 Fm
0.1 Fm
0.1 Fm
+V
S
-V
S
V
O
V
D
V
I
R
G
R
F
1/2
OPA2690
+5V
DIS
698W
100W
698W
50W
402W
402W
0.1 Fm
0.1 Fm
59W
+
6.8 Fm0.1 Fm
+V
S
V
S
/2
V
O
V
D
V
I
R
G
R
F
OPA2690
SBOS238G –JUNE 2002–REVISED MARCH 2010 www.ti.com
APPLICATION INFORMATION
WIDEBAND VOLTAGE-FEEDBACK output swing on a single +5V supply with > 150MHz
OPERATION bandwidth. The key requirement of broadband
single-supply operation is to maintain input and
The OPA2690 provides an exceptional combination
output signal swings within the usable voltage ranges
of high output power capability in a wideband,
at both the input and the output. The circuit of
unity-gain stable voltage-feedback op amp using a
Figure 37 establishes an input midpoint bias using a
new high slew rate input stage. Typical differential
simple resistive divider from the +5V supply (two
input stages used for voltage feedback op amps are
698Ω resistors). Separate bias networks would be
designed to steer a fixed-bias current to the
required at each input. The input signal is then
compensation capacitor, setting a limit to the
ac-coupled into the midpoint voltage bias. The input
achievable slew rate. The OPA2690 uses a new input
voltage can swing to within 1.5V of either supply pin,
stage that places the transconductance element
giving a 2V
PP
input signal range centered between
between two input buffers, using their output currents
the supply pins. The input impedance matching
as the forward signal. As the error voltage increases
resistor (59Ω) used for testing is adjusted to give a
across the two inputs, an increasing current is
50Ω input load when the parallel combination of the
delivered to the compensation capacitor. This
biasing divider network is included.
provides very high slew rate (1800V/ms) while
consuming relatively low quiescent current
(5.5mA/ch). This exceptional, full-power performance
comes at the price of a slightly higher input noise
voltage than alternative architectures. The 5.5nV/√Hz
input voltage noise for the OPA2690 is exceptionally
low for this type of input stage.
Figure 36 shows the dc-coupled, gain of +2, dual
power supply circuit configuration used as the basis
of the ±5V Electrical Characteristics and Typical
Characteristics. This is for one channel; the other
channel is connected similarly. For test purposes, the
input impedance is set to 50Ω with a resistor to
ground and the output impedance is set to 50Ω with a
series output resistor. Voltage swings reported in the
Electrical Characteristics are taken directly at the
input and output pins, while output powers (dBm) are
at the matched 50Ω load. For the circuit of Figure 36,
the total effective load will be 100Ω || 804Ω. The
disable control line (SO-14 package only) is typically
Figure 36. DC-Coupled, G = +2, Bipolar-Supply
left open for normal amplifier operation. Two optional Specification and Test Circuit
components are included in Figure 36. An additional
resistor (175Ω) is included in series with the
noninverting input. Combined with the 25Ω dc source
resistance looking back towards the signal generator,
this gives an input bias current cancelling resistance
that matches the 200Ω source resistance seen at the
inverting input (see the DC Accuracy and Offset
Control section). In addition to the usual power-supply
decoupling capacitors to ground, a 0.1mF capacitor is
included between the two power-supply pins. In
practical printed circuit board (PCB) layouts, this
optional-added capacitor will typically improve the
2nd-harmonic distortion performance by 3dB to 6dB.
Figure 37 shows the ac-coupled, gain of +2,
single-supply circuit configuration used as the basis
of the +5V Electrical Characteristics and Typical
Characteristics. Though not a rail-to-rail design, the
OPA2690 requires minimal input and output voltage
Figure 37. AC-Coupled, G = +2, Single-Supply
headroom compared to other very wideband
Specification and Test Circuit
voltage-feedback op amps. It will deliver a 3V
PP
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Product Folder Link(s): OPA2690