OP467_07 Datasheet, PDF (14/20 Pages) Analog Devices – Quad Precision, High Speed Operational Amplifier

OP467
amplifier. Stray capacitance on the PCB can be reduced by making
the traces narrow and as short as possible. Further reduction
can be realized by choosing a smaller pad size, increasing the
spacing between the traces, and using PCB material with a low
dielectric constant insulator (dielectric constant of some common
insulators: air = 1, Teflon® = 2.2, and FR4 = 4.7, with air being
an ideal insulator).
Removing segments of the ground plane directly under the
input and output pads is recommended.
Outputs of high speed amplifiers are very sensitive to capacitive
loads. A capacitive load introduces a pair of pole and zero to the
frequency response of the circuit, reducing the phase margin,
leading to unstable operation or oscillation.
Generally, it is good design practice to isolate the output of the
amplifier from any capacitive load by placing a resistor between
the output of the amplifier and the rest of the circuits. A series
resistor of 10 Ω to 100 Ω is normally sufficient to isolate the
output from a capacitive load.
The OP467 is internally compensated to provide stable
operation and is capable of driving large capacitive loads
without oscillation.
Sockets are not recommended because they increase the lead
inductance/capacitance and reduce the power dissipation of the
package by increasing the thermal resistance of the leads. If
sockets must be used, use Teflon or pin sockets with the shortest
possible leads.
PHASE REVERSAL
The OP467 is immune to phase reversal; its inputs can exceed
the supply rails by a diode drop without any phase reversal.
100
OUTPUT 90
ΔV1
15.8V
10
INTPUT _0%
10V
10V
200µs
Figure 41. No Phase Reversal (AV = +1)
SATURATION RECOVERY TIME
The OP467 has a fast and symmetrical recovery time from
either rail. This feature is very useful in applications such as
high speed instrumentation and measurement circuits, where
the amplifier is frequently exposed to large signals that overload
the amplifier.
DLY 9.824µs
100
90
10
0%
5V
5V
20ns
Figure 42. Saturation Recovery Time, Positive Rail
DLY 4.806µs
100
90
10
0%
5V
5V
20ns
Figure 43. Saturation Recovery Time, Negative Rail
HIGH SPEED INSTRUMENTATION AMPLIFIER
The OP467 performance lends itself to a variety of high speed
applications, including high speed precision instrumentation
amplifiers. Figure 44 represents a circuit commonly used for
data acquisition, CCD imaging, and other high speed
applications.
The circuit gain is set by RG. A 2 kΩ resistor sets the circuit gain
to 2; for unity gain, remove RG. For any other gain settings, use
the following formula
G = 2/RG (Resistor Value is in kΩ)
RC is used for adjusting the dc common-mode rejection, and CC
is used for ac common-mode rejection adjustments.
–V_IN
C_C
2kΩ
1kΩ
2kΩ
+V_IN
R_{G 10kΩ}
1kΩ
10kΩ
2kΩ
5pF
OUTPUT
1.9kΩ
R_C
200Ω
10T
Figure 44. A High Speed Instrumentation Amplifier
Rev. F | Page 14 of 20