EL8178FSZ 查看數據表（PDF） - Intersil
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EL8178FSZ Datasheet PDF : 15 Pages
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EL8178
Pin Descriptions
SO PIN
NUMBER
1
2
3
4
5
6
7
8
SOT-23 PIN 6 Ld WLCSP
NUMBER PIN NUMBER
A1
4
C1
3
C2
2
B2
1
A2
6
B1
5
EQUIVALENT
PIN NAME CIRCUIT
DESCRIPTION
NC
No internal connection
IN-
Circuit 1 Amplifier’s inverting input
IN+
Circuit 1 Amplifier’s non-inverting input
V-
Circuit 4 Negative power supply
NC
No internal connection
OUT
Circuit 3 Amplifier’s output
V+
Circuit 4 Positive power supply
EN
Circuit 2 Amplifier’s enable pin with internal pull-down; Logic “1” selects the
disabled state; Logic “0” selects the enabled state.
V+
V+
IN-
IN+
EN
V-
V-
V+
V+
OUT
V-
V-
CAPACITIVELY
COUPLED
ESD CLAMP
CIRCUIT 1
CIRCUIT 2
CIRCUIT 3
CIRCUIT 4
Application Information
Introduction
The EL8178 is a rail-to-rail input and output (RRIO),
micropower, precision, single supply op amp with an enable
feature. This amplifier is designed to operate from single
supply (2.4V to 5.5V) or dual supply (±1.2V to ±2.75V) while
drawing only 55µA of supply current.The device achieves
rail-to-rail input and output operation while eliminating the
drawbacks of many conventional RRIO op amps.
Rail-to-Rail Input
The PFET input stage of the EL8178 has an input
common-mode voltage range that includes the negative and
positive supplies without introducing offset errors or
degrading performance like some existing rail-to-rail input
op amps. Many rail-to-rail input stages use two differential
input pairs: a long-tail PNP (or PFET) and an NPN (or
NFET). Severe penalties result from using this topology. As
the input signal moves from one supply rail to the other, the
op amp switches from one input pair to the other causing
changes in input offset voltage and an undesired change in
the input offset current’s magnitude and polarity.
The EL8178 achieves rail-to-rail input performance without
sacrificing important precision specifications and without
degrading distortion performance. The EL8178's input offset
voltage exhibits a smooth behavior throughout the entire
common-mode input range.
Rail-to-Rail Output
A pair of complementary MOSFET devices achieve rail-to-rail
output swing. The NMOS sinks current to swing the output in
the negative direction, while the PMOS sources current to
swing the output in the positive direction. The EL8178 with a
100kΩ load swings to within 3mV of the supply rails.
Results of Overdriving the Output
Caution should be used when overdriving the output for long
periods of time. Overdriving the output can occur in three ways:
1. The input voltage times the gain of the amplifier exceeds the
supply voltage by a large value.
2. The output current required is higher than the output stage
can deliver.
3. Operating the device in slew rate limit. These conditions can
result in a shift in the Input Offset Voltage (VOS) as much as
1µV/hr of exposure under these conditions.
Enable/Disable Feature
The EL8178 features an active low EN pin that when pulled
up to at least 2V, disables the output and drops the ICC to a
3µA. The EN pin has an internal pull-down, so an undriven
pin pulls to the negative rail, thereby enabling the op amp by
default. For applications where the EN pin is not being used,
it is recommended that the EN pin be permanently tyed to
ground.
The high impedance output during disable allows for
connecting multiple EL8178s together to implement a Mux
Amp. The outputs are connected together and activating the
appropriate EN pin selects the desired channel. If utilizing
non-unity gain op amp configurations, then the loading
10
FN7504.6
March 17, 2008
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