IC, OP-AMP, 100MHZ, 3000V/µs, SOIC-8

LM6172IMX

Manufacturer Part NumberLM6172IMX
DescriptionIC, OP-AMP, 100MHZ, 3000V/µs, SOIC-8
ManufacturerNational Semiconductor
LM6172IMX datasheet
 


Specifications of LM6172IMX

Op Amp TypeLow PowerNo. Of Amplifiers2
Bandwidth100MHzSlew Rate3000V/µs
Supply Voltage Range5.5V To 36VAmplifier Case StyleSOIC
No. Of Pins8Lead Free Status / RoHS StatusContains lead / RoHS non-compliant
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Application Notes
(Continued)
FIGURE 2. The LM6172 Driving a 510pF Load
with a 30Ω Isolation Resistor
FIGURE 3. The LM6172 Driving a 220 pF Load
with a 50Ω Isolation Resistor
LAYOUT CONSIDERATION
PRINTED CIRCUIT BOARDS AND HIGH SPEED OP
AMPS
There are many things to consider when designing PC
boards for high speed op amps. Without proper caution, it is
very easy to have excessive ringing, oscillation and other
degraded AC performance in high speed circuits. As a rule,
the signal traces should be short and wide to provide low
inductance and low impedance paths. Any unused board
space needs to be grounded to reduce stray signal pickup.
Critical components should also be grounded at a common
point to eliminate voltage drop. Sockets add capacitance to
the board and can affect frequency performance. It is better
to solder the amplifier directly into the PC board without
using any socket.
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USING PROBES
Active (FET) probes are ideal for taking high frequency
measurements because they have wide bandwidth, high
input impedance and low input capacitance. However, the
probe ground leads provide a long ground loop that will
produce errors in measurement. Instead, the probes can be
grounded directly by removing the ground leads and probe
jackets and using scope probe jacks.
COMPONENTS SELECTION AND FEEDBACK
RESISTOR
It is important in high speed applications to keep all compo-
nent leads short because wires are inductive at high fre-
quency.
For
discrete
composition-type resistors and mica-type capacitors. Sur-
face mount components are preferred over discrete compo-
nents for minimum inductive effect.
Large values of feedback resistors can couple with parasitic
capacitance and cause undesirable effects such as ringing
01258152
or oscillation in high speed amplifiers. For LM6172, a feed-
back resistor less than 1kΩ gives optimal performance.
COMPENSATION FOR INPUT CAPACITANCE
The combination of an amplifier’s input capacitance with the
gain setting resistors adds a pole that can cause peaking or
oscillation. To solve this problem, a feedback capacitor with
a value
>
C
F
can be used to cancel that pole. For LM6172, a feedback
capacitor of 2pF is recommended. Figure 4 illustrates the
compensation circuit.
FIGURE 4. Compensating for Input Capacitance
15
components,
choose
carbon
(R
x C
)/R
G
IN
F
01258146
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