HCA10014 Datasheet, PDF (7/17 Pages) Intersil Corporation – 15MHz, BiMOS Operational Amplifier with MOSFET Input/CMOS Output

HCA10014
common mode input voltage at T_A = 25^oC. These data show
that circuit designers can advantageously exploit these
characteristics to design circuits which typically require an
input current of less than 1pA, provided the common mode
input voltage does not exceed 2V. As previously noted, the
input current is essentially the result of the leakage current
through the gate protection diodes in the input circuit and,
therefore, a function of the applied voltage. Although the
finite resistance of the glass terminal-to-case insulator of the
metal can package also contributes an increment of leakage
current, there are useful compensating factors.
4000
1000
V_S = ±7.5V
100
10
10
T_A = 25^oC
7.5
15V
V+ _TO
5V
7
5
2
PA
6
3
2.5
8
V_IN
4
0V
TO
-10V
0
V-
-1 0 1 2 3 4 5 6 7
INPUT CURRENT (pA)
FIGURE 9. INPUT CURRENT vs COMMON-MODE VOLTAGE
Offset Nulling
Offset voltage nulling is usually accomplished with a
100,000Ω potentiometer connected across Terminals 1 and
5 and with the potentiometer slider arm connected to
Terminal 4. A fine offset null adjustment usually can be
effected with the slider arm positioned in the midpoint of the
potentiometer’s total range.
Input Current Variation with Temperature
The input current of the HCA10014 circuit is typically 5pA at
25^oC. The major portion of this input current is due to
leakage current through the gate protective diodes in the
input circuit. As with any semiconductor junction device,
including op amps with a junction FET input stage, the
leakage current approximately doubles for every 10^oC
increase in temperature. Figure 10 provides data on the
typical variation of input bias current as a function of
temperature.
1
-80 -60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (^oC)
FIGURE 10. INPUT CURRENT vs TEMPERATURE
Input Offset Voltage (VIO) Variation with DC Bias
and Device Operating Life
It is well known that the characteristics of a MOSFET device
can change slightly when a DC gate source bias potential is
applied to the device for extended time periods. The
magnitude of the change is increased at high temperatures.
Users should be alert to the possible impacts of this effect if
the application of the device involves extended operation at
high temperatures with a significant differential DC bias
voltage applied across Terminals 2 and 3. Figure 11 shows
typical data pertinent to shifts in offset voltage encountered
with devices during life testing. At lower temperatures (metal
can and plastic), for example at 85^oC, 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. The 2V_DC differential voltage
example represents conditions when the amplifier output
stage is “toggled”, e.g., as in comparator applications.
7
6
DIFFERENTIAL DC VOLTAGE
5
(ACROSS TERMINALS 2 AND 3) = 2V
OUTPUT STAGE TOGGLED
4
3
2
DIFFERENTIAL DC VOLTAGE
1
(ACROSS TERMINALS 2 AND 3) = 0V
OUTPUT VOLTAGE = V+ /2
0
0 500 1000 1500 2000 2500 3000 3500 4000
TIME (HOURS)
FIGURE 11. TYPICAL INCREMENTAL OFFSET VOLTAGE
SHIFT vs OPERATING LIFE
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