Datasheet

APPLICATIONS INFORMATION
WIDEBAND VOLTAGE-FEEDBACK
1/2
OPA2830
V
S
= +3V
V
OUT
53.6
Ω
V
IN
2.26k
Ω
1.13k
Ω
R
L
150
Ω
+V
S
3
6.8
µ
F
+
0.1
µ
F
0.1
µ
F
R
F
750
Ω
R
G
750
Ω
+1V
+V
S
/3
1/2
OPA2830
V
S
= +5V
V
OUT
53.6
Ω
V
IN
1.5k
Ω
+V
S
/2
1.5k
Ω
R
L
150
Ω
+V
S
2
6.8
µ
F
+
0.1
µ
F
0.1
µ
F
R
F
750
Ω
R
G
750
Ω
2.5V
OPA2830
SBOS309D – AUGUST 2004 – REVISED AUGUST 2008 .................................................................................................................................................. www.ti.com
high frequencies is 150 Ω || 1500 Ω . The 1.13k Ω and
2.26k Ω resistors at the noninverting input provide the
common-mode bias voltage. Their parallel
OPERATION
combination equals the DC resistance at the inverting
The OPA2830 is a unity-gain stable, very high-speed
input (R
F
), reducing the DC output offset due to input
voltage-feedback op amp designed for single-supply
bias current.
operation (+3V to +10V). The input stage supports
input voltages below ground and to within 1.7V of the
positive supply. The complementary common-emitter
output stage provides an output swing to within 25mV
of ground and the positive supply. The OPA2830 is
compensated to provide stable operation with a wide
range of resistive loads.
Figure 70 shows the AC-coupled, gain of +2
configuration used for the +5V Specifications and
Typical Characteristic Curves. For test purposes, the
input impedance is set to 50 Ω with a resistor to
ground. Voltage swings reported in the Electrical
Characteristics are taken directly at the input and
output pins. For the circuit of Figure 70 , the total
effective load on the output at high frequencies is
150 Ω || 1500 Ω . The 1.5k Ω resistors at the
noninverting input provide the common-mode bias
voltage. Their parallel combination equals the DC
resistance at the inverting input (R
F
), reducing the DC
output offset due to input bias current.
Figure 71. AC-Coupled, G = +2, +3V Single-Supply
Specification and Test Circuit
Figure 72 shows the DC-coupled, gain of +2, dual
power-supply circuit configuration used as the basis
of the ± 5V Electrical Characteristics and Typical
Characteristics. For test purposes, the input
impedance is set to 50 Ω with a resistor to ground and
the output impedance is set to 150 Ω with a series
output resistor. Voltage swings reported in the
specifications are taken directly at the input and
output pins. For the circuit of Figure 72 , the total
effective load will be 150 Ω || 1.5k Ω . Two optional
components are included in Figure 72 . An additional
resistor (348 Ω ) is included in series with the
noninverting input. Combined with the 25 Ω DC
source resistance looking back towards the signal
generator, this gives an input bias current cancelling
resistance that matches the 375 Ω source resistance
seen at the inverting input (see the DC Accuracy and
Figure 70. AC-Coupled, G = +2, +5V Single-Supply
Offset Control section). In addition to the usual
Specification and Test Circuit
power-supply decoupling capacitors to ground, a
0.01 µ F capacitor is included between the two
power-supply pins. In practical PC board layouts, this
Figure 71 shows the AC-coupled, gain of +2
optional capacitor will typically improve the
configuration used for the +3V Specifications and
2nd-harmonic distortion performance by 3dB to 6dB.
Typical Characteristic Curves. Voltage swings
reported in the Electrical Characteristics are taken
directly at the input and output pins. For the circuit of
Figure 71 , the total effective load on the output at
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