Datasheet

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SBOS146A − OCTOBER 1986 − REVISED AUGUST 2004
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13
OPTIONAL BANDWIDTH CONTROL
Low-pass filtering is recommended where possible and
can be done by either one of two techniques; see
Figure 12. C
2
connected to pins 3 and 4 will reduce the
bandwidth with a cutoff frequency given by:
f
CO
+
15.9
(
R
1
) R
2
) R
3
) R
4
)(
C
2
) 3pF
)
This method has the disadvantage of having f
CO
vary with
R
1
, R
2
, R
3
, R
4
, and it may require large values of R
3
and
R
4
. The other method, using C
1
, will use smaller values of
capacitance and is not a function of the input resistors. It
is, however, more subject to nonlinear distortion caused by
slew rate limiting. This is normally not a problem with the
slow signals associated with most process control
transducers. The relationship between C
1
and f
CO
is
shown in the Typical Characteristics.
3
4
+
−
XTR101
1mA
13
12
NOTE: (1) R
3
and R
4
should be equal if used.
1mA
R
2
11
0.0047
µ
F
C
1
R
4
(1)
R
3
(1)
C
2
R
1
Gain
e
2
OUTPUT STAGE
Internally e
NOISE RTI
=e
2
INPUT STAGE
+
2
Figure 12. Optional Filtering
APPLICATION CIRCUITS
XTR101
R
2
500
Ω
100pF
MC1403A
OPA27
V
R
=2.5V
+
−
V
−
V+
I
O
(4−20 mA)
I
O
(0−20mA)
R
1
125
Ω
NOTE:
Other conversions are readily achievable by
changing the reference and ratio of R
1
to R
2
.
Voltage
Reference
I
O
+
ǒ
1 )
R
1
R
2
Ǔ
I
O
*
V
R
R
2
+ 1.25 I
O
* 5mA
Ȁ
Ȁ
Figure 13. 0-20mA Output Converter