sm72501mfx National Semiconductor Corporation, sm72501mfx Datasheet - Page 15

• Manufacturer Part Number: sm72501mfx
• Description: Solarmagic Precision, Cmos Input, Rrio, Wide Supply Range Amplifier
• Manufacturer: National Semiconductor Corporation

Equation 1
pairs of poles that causes gain peaking. In order to eliminate
this effect, the poles should be placed in Butterworth position,
since poles in Butterworth position do not cause gain peaking.
To achieve a Butterworth pair, the quantity under the square
root in
and the relation between R
value for R
is chosen to be larger than this optimum value, gain peaking
will occur.
In
and to increase stability. Additionally, C
nates the gain peaking that can be caused by having a larger
feedback resistor.
ing.
Figure
FIGURE 4. Closed Loop Gain vs. Frequency with
FIGURE 3. Closed Loop Gain vs. Frequency
Equation 1
2, C
1
has two poles. In most cases, it is the presence of
can be found. This is shown in
F
is added to compensate for input capacitance
Figure 4
should be set to equal −1. Using this fact
Compensation
1
shows how C
and R
2
, R
2
= −A
F
F
reduces gain peak-
V
reduces or elimi-
Equation
R
1
, the optimum
30142154
30142155
2. If R
(2)
1
15
DIODES BETWEEN THE INPUTS
The SM72501 has a set of anti-parallel diodes between the
input pins, as shown in
protect the input stage of the amplifier. At the same time, they
limit the amount of differential input voltage that is allowed on
the input pins. A differential signal larger than one diode volt-
age drop might damage the diodes. The differential signal
between the inputs needs to be limited to ±300 mV or the input
current needs to be limited to ±10 mA.
FIGURE 5. Input of SM72501
Figure
5. These diodes are present to
www.national.com
30142125