CA3140, CA3140A
the CA3140 is used as a unity gain voltage follower. This
resistance prevents the possibility of extremely large input
signal transients from forcing a signal through the input
protection network and directly driving the internal constant
current source which could result in positive feedback via the
output terminal. A 3.9kΩ resistor is sufficient.
The typical input current is on the order of 10pA when the
inputs are centered at nominal device dissipation. As the
output supplies load current, device dissipation will increase,
raising the chip temperature and resulting in increased input
current. Figure 7 shows typical input terminal current versus
ambient temperature for the CA3140.
It is well known that MOSFET devices can exhibit slight
changes in characteristics (for example, small changes in
OPEN LOOP PHASE
(DEGREES)
input offset voltage) due to the application of large
differential input voltages that are sustained over long
periods at elevated temperatures.
Both applied voltage and temperature accelerate these
changes. The process is reversible and offset voltage shifts of
the opposite polarity reverse the offset. Figure 9 shows the
typical offset voltage change as a function of various stress
voltages at the maximum rating of 125
o
C (for metal can); at
lower temperatures (metal can and plastic), for example, at
85
o
C, this change in voltage is considerably less. In typical
linear applications, where the differential voltage is small and
symmetrical, these incremental changes are of about the
same magnitude as those encountered in an operational
amplifier employing a bipolar transistor input stage.
OPEN LOOP VOLTAGE GAIN (dB)
SUPPLY VOLTAGE: V
S
=
±15V
T
A
= 25
o
C
100
80
60
40
20
0
10
1
R
L
= 2kΩ,
C
L
= 100pF
φOL
-75
R
L
= 2kΩ,
C
L
= 0pF
-90
-105
-120
-135
-150
10K
SUPPLY VOLTAGE: V
S
=
±15V
INPUT CURRENT (pA)
1K
100
10
10
2
10
3
10
4
10
5
10
6
FREQUENCY (Hz)
10
7
10
8
1
-60
-40
-20
0
20
40
60
80
TEMPERATURE (
o
C)
100
120
140
FIGURE 6. OPEN LOOP VOLTAGE GAIN AND PHASE vs
FREQUENCY
FIGURE 7. INPUT CURRENT vs TEMPERATURE
INPUT AND OUTPUT VOLTAGE EXCURSIONS
FROM TERMINAL 7 (V+)
R
L
=
∞
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
+V
ICR
AT T
A
= 125
o
C
+V
ICR
AT T
A
= 25
o
C
+V
ICR
AT T
A
= -55
o
C
+V
OUT
AT T
A
= 125
o
C
+V
OUT
AT T
A
= 25
o
C
+V
OUT
AT T
A
= -55
o
C
INPUT AND OUTPUT VOLTAGE EXCURSIONS
FROM TERMINAL 4 (V-)
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-V
OUT
FOR
T
A
= -55
o
C to 125
o
C
-V
ICR
AT T
A
= 125
o
C
-V
ICR
AT T
A
= 25
o
C
-V
ICR
AT T
A
= -55
o
C
0
5
10
15
SUPPLY VOLTAGE (V+, V-)
20
25
0
5
10
15
SUPPLY VOLTAGE (V+, V-)
20
25
FIGURE 8. OUTPUT VOLTAGE SWING CAPABILITY AND COMMON MODE INPUT VOLTAGE RANGE vs SUPPLY VOLTAGE
9
FN957.10
July 11, 2005
INTERSIL [ INTERSIL CORPORATION ]
