LTC6084 查看數據表（PDF） - Linear Technology
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LTC6084 Datasheet PDF : 16 Pages
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LTC6084/LTC6085
APPLICATIONS INFORMATION
SHDN Pins
Pins 5 and 6 are used for power shutdown of the LTC6084
in the DD package. If they are floating, internal current
sources pull pins 5 and 6 to V+ and the amplifiers operate
normally. In shutdown the amplifier output is high imped-
ance, and each amplifier draws less than 1μA current.
This feature allows the part to be used in muxed output
applications as shown in Figure 3.
10k
5V
10k
INA
10k
5V
+
A
–
SHDN
A
10k
LTC6084
(DD PACKAGE)
10k
5V
10k
10k
INB
SEL
+
B
–
OUT
SEL = 5V, OUT = –INA
SEL = 0V, OUT = –INB
10k
5V
SHDN
B
FAIRCHILD
NC7SZ04 OR
EQUIVALENT 60845 F03
Figure 3. Inverting Amplifier with Muxed Output
ESD
The LTC6084/LTC6085 has reverse-biased ESD protection
diodes on all inputs and outputs as shown in the Simpli-
fied Schematic. If these pins are forced beyond either
supply, unlimited current will flow through these diodes.
If the current is transient and limited to 100mA or less,
no damage to the device will occur.
The amplifier input bias current is the leakage current of
these ESD diodes. This leakage is a function of the tem-
perature and common mode voltage of the amplifier, as
shown in the Typical Performance Characteristics.
Noise
In the frequency region above 1kHz, the LTC6084/LTC6085
shows good noise voltage performance. In this region,
noise can be dominated by the total source resistance of the
particular application. Specifically, these amplifiers exhibit
the noise of a 58k resistor, meaning it is desirable to keep
the source and feedback resistance at or below this value,
i.e., RS + RG||RFB ≤ 58k. Above this total source impedance,
the noise voltage is dominated by the resistors.
At low frequency, noise current can be estimated from the
expression in = √2qIB, where q = 1.6 • 10–19 coulombs.
Equating √4kTRΔf and R√2qIBΔf shows that for a source
resistor below 50GΩ the amplifier noise is dominated by
the source resistance. Noise current rises with frequency.
See the curve Input Noise Current vs Frequency in the
Typical Performance Characteristics section.
60845f
11
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