LMC6022IM NSC [National Semiconductor], LMC6022IM Datasheet - Page 10

• Manufacturer Part Number: LMC6022IM
• Description: Low Power CMOS Dual Operational Amplifier
• Manufacturer: NSC [National Semiconductor]

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Application Hints
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
BIAS CURRENT TESTING
The test method of Figure 7 is appropriate for bench-testing
bias current with reasonable accuracy. To understand its op-
eration, first close switch S2 momentarily. When S2 is
opened, then
Typical Single-Supply Applications
Note: A 5V bias on the photodiode can cut its capacitance by a factor of 2
or 3, leading to improved response and lower noise. However, this bias on
the photodiode will cause photodiode leakage (also known as its dark
current).
Photodiode Current-to-Voltage Converter
FIGURE 6. Air Wiring
(Continued)
DS011236-15
DS011236-13
(V+ = 5.0 V
(Upper limit of output range dictated by input common-mode range; lower
limit dictated by minimum current requirement of LM385.)
10
A suitable capacitor for C2 would be a 5 pF or 10 pF silver
mica, NPO ceramic, or air-dielectric. When determining the
magnitude of I
must be taken into account. Switch S2 should be left shorted
most of the time, or else the dielectric absorption of the ca-
pacitor C2 could cause errors.
Similarly, if S1 is shorted momentarily (while leaving S2
shorted)
where C
FIGURE 7. Simple Input Bias Current Test Circuit
DC
x
)
Micropower Current Source
is the stray capacitance at the + input.
−
, the leakage of the capacitor and socket
DS011236-16
DS011236-14