ISL28276 Datasheet, PDF (10/12 Pages) Intersil Corporation – Dual Precision Micropower Single Supply Rail-to-Rail Input and Output Precision Op-Amps

ISL28276
Pin Descriptions
ISL28276
EQUIVALENT
(16 LD QSOP) PIN NAME CIRCUIT
DESCRIPTION
1
NC
No internal connection
2
NC
No internal connection
3
OUT_A
Circuit 3 Amplifier A output
4
IN-_A
Circuit 1 Amplifier A inverting input
5
IN+_A
Circuit 1 Amplifier A non-inverting input
6
EN_A
Circuit 2 Amplifier A enable pin internal pull-down; Logic “1” selects the disabled state; Logic “0” selects
the enabled state.
7
V-
Circuit 4 Negative power supply
8
NC
No internal connection
9
NC
No internal connection
10
NC
No internal connection
11
EN_B
Circuit 2 Amplifier B enable pin with internal pull-down; Logic “1” selects the disabled state; Logic “0”
selects the enabled state.
12
IN+_B
Circuit 1 Amplifier B non-inverting input
13
IN-_B
Circuit 1 Amplifier B inverting input
14
OUT_B
Circuit 3 Amplifier B output
15
V+
Circuit 4 Positive power supply
16
NC
No internal connection
IN-
CIRCUIT 1
V+
IN+
V-
V+
LOGIC
PIN
V-
CIRCUIT 2
V+
OUT
V-
CIRCUIT 3
V+
CAPACITIVELY
COUPLED
ESD CLAMP
V-
CIRCUIT 4
Applications Information
Introduction
The ISL28276 is an enhanced rail-to-rail input micropower
precision operational amplifiers with an enable feature. The
part is designed to operate from single supply (2.4V to 5.0V)
or dual supply (±1.2V to ±2.5V). The device is capable of
swinging 0.5V above a 5.0V supply (0.25V for a 2.4V supply)
and to within 10mV from ground. The ISL28276 maintains
CMRR performance for input voltages greater than the
positive supply. The output operation can swing within about
3mV of the supply rails with a 100kΩ load (reference
Figures 29 through 32).
Rail-to-Rail Input
The input common-mode voltage range of the ISL28276
goes from negative supply to positive supply without
introducing additional offset errors or degrading performance
associated with a conventional rail-to-rail input operational
10
amplifier. Many rail-to-rail input stages use two differential
input pairs, a long-tail PNP (or PFET) and an NPN (or
NFET). Severe penalties have to be paid for this circuit
topology. As the input signal moves from one supply rail to
another, the operational amplifier switches from one input
pair to the other causing drastic changes in input offset
voltage and an undesired change in magnitude and polarity
of input offset current.
The ISL28276 achieves input rail-to-rail without sacrificing
important precision specifications and degrading distortion
performance. The devices’ input offset voltage exhibits a
smooth behavior throughout the entire common-mode input
range. The input bias current versus the common-mode
voltage range gives us an undistorted behavior from typically
10mV above the negative rail and 10% higher than the V+
rail (0.5V higher than V+ when V+ equals 5v).
FN6301.0
June 23, 2006