LM359M National Semiconductor, LM359M Datasheet - Page 10

• Manufacturer Part Number: LM359M
• Description: IC AMP DUAL PROG CUR MODE 14SOIC
• Manufacturer: National Semiconductor

Specifications of LM359M

• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Slew Rate: 60 V/µs
• Gain Bandwidth Product: 400MHz
• Current - Input Bias: 8µA
• Current - Supply: 18.5mA
• Current - Output / Channel: 40mA
• Voltage - Supply, Single/dual (±): 5 V ~ 22 V, ±2.5 V ~ 11 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Output Type: -
• -3db Bandwidth: -
• Voltage - Input Offset: -
• Other names: *LM359M

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Application Hints
Pin 1 must never be shorted to ground or pin 8 never shorted
to V
catastrophic device failure.
CONSIDERATIONS FOR HIGH FREQUENCY
OPERATION
The LM359 is intended for use in relatively high frequency
applications and many factors external to the amplifier itself
must be considered. Minimization of stray capacitances and
their effect on circuit operation are the primary requirements.
The following list contains some general guidelines to help
accomplish this end:
1. Keep the leads of all external components as short as
2. Place components conducting signal current from the
3. Use reasonably low value resistances for gain setting
4. Use of a ground plane is helpful in providing a shielding
5. Use a single-point ground and single-point supply distri-
6. Avoid use of long wires (
7. Bypass the supply close to the device with a low induc-
COMPENSATION
The LM359 is internally compensated for stability with closed
loop inverting gains of 10 or more. For an inverting gain of
less than 10 and all non-inverting amplifiers (the amplifier
always has 100% negative current feedback regardless of
the gain in the non-inverting configuration) some external
frequency compensation is required because the stray ca-
pacitance to ground from the (−) input and the feedback
resistor add additional lagging phase within the feedback
loop. The value of the input capacitance will typically be in
the range of 6 pF to 10 pF for a reasonably constructed
circuit board. When using a feedback resistance of 30 kΩ or
less, the best method of compensation, without sacrificing
slew rate, is to add a lead capacitor in parallel with the
feedback resistor with a value on the order of 1 pF to 5 pF as
shown in Figure 10 .
+
possible.
output of an amplifier away from that amplifier’s non-
inverting input.
and biasing.
effect between the inputs and from input to output. Avoid
using vector boards.
bution to minimize crosstalk. Always connect the two
grounds (one from each amplifier) together.
shielded wire.
tance, low value capacitor (typically a 0.01 µF ceramic)
to create a good high frequency ground. If long supply
leads are unavoidable, a small resistor (∼10Ω) in series
with the bypass capacitor may be needed and using
shielded wire for the supply leads is also recommended.
without limiting the current to 2 mA or less to prevent
>
(Continued)
2") but if necessary, use
10
C
Another method of compensation is to increase the effective
value of the internal compensation capacitor by adding ca-
pacitance from the COMP pin of an amplifier to ground. An
external 20 pF capacitor will generally compensate for all
gain settings but will also reduce the gain bandwidth product
and the slew rate. These same results can also be obtained
by reducing I
not required. This method is termed over-compensation.
Another area of concern from a stability standpoint is that of
capacitive loading. The amplifier will generally drive capaci-
tive loads up to 100 pF without oscillation problems. Any
larger C loads can be isolated from the output as shown in
Figure 11. Over-compensation of the amplifier can also be
used if the corresponding reduction of the GBW product can
be afforded.
In most applications using the LM359, the input signal will be
AC coupled so as not to affect the DC biasing of the ampli-
fier. This gives rise to another subtlety of high frequency
circuits which is the effective series inductance (ESL) of the
coupling capacitor which creates an increase in the imped-
ance of the capacitor at high frequencies and can cause an
unexpected gain reduction. Low ESL capacitors like solid
tantalum for large values of C and ceramic for smaller values
are recommended. A parallel combination of the two types is
even better for gain accuracy over a wide frequency range.
f
= 1 pF to 5 pF for stability
FIGURE 11. Isolating Large Capacitive Loads
FIGURE 10. Best Method of Compensation
SET(IN)
if the full capabilities of the amplifier are
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