LT1783 Linear Technology, LT1783 Datasheet - Page 9

• Manufacturer Part Number: LT1783
• Description: 1.25MHz/ Over-The-Top Micropower/ Rail-to-Rail Input and Output Op Amp in SOT-23
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
input bias current is typically 80nA. Increases in tempera-
ture will cause the voltage at which operation switches
from the PNP input stage to the NPN input stage to move
towards V
untrimmed and is typically 1.8mV.
A Schottky diode in the collector of the input transistors,
along with special geometries for these NPN transistors,
allow the LT1783 to operate with either or both of its inputs
above V
tor is fully saturated and the input bias current is typically
30 A at room temperature. The input offset voltage is
typically 1.8mV when operating above V
operate with its inputs 18V above V
The inputs are protected against excursions as much as
10V below V
input and a diode from the input to the negative supply.
The input stage of the LT1783 incorporates phase reversal
protection to prevent the output from phase reversing for
inputs up to 9V below V
between the inputs and the maximum differential input
voltage is 18V.
Output
The output of the LT1783 can swing to within 60mV of the
positive rail with no load and within 3mV of the negative
rail with no load. When monitoring input voltages within
60mV of the positive rail or within 3mV of the negative rail,
gain should be taken to keep the output from clipping. The
LT1783 can sink and source over 30mA at 5V supplies,
sourcing current is reduced to 10mA at 3V total supplies
as noted in the Electrical Characteristics.
The LT1783 is internally compensated to drive at least
400pF of capacitance under any output loading condi-
tions. A 0.22 F capacitor in series with a 150 resistor
between the output and ground will compensate these
amplifiers for larger capacitive loads, up to 10,000pF, at all
output currents.
+
. At about 0.3V above V
+
. The input offset voltage of the NPN stage is
–
by an internal 1k resistor in series with each
U
–
. There are no clamping diodes
U
+
, the NPN input transis-
W
–
regardless of V
+
. The LT1783 will
U
+
.
Distortion
There are two main contributors to distortion in op amps:
output crossover distortion as the output transitions from
sourcing to sinking current, and distortion caused by
nonlinear common mode rejection. If the op amp is
operating inverting, there is no common mode induced
distortion. If the op amp is operating in the PNP input stage
(input is not within 0.8V of V
typically 100dB. When the LT1783 switches between
input stages, there is significant nonlinearity in the CMRR.
Lower load resistance increases the output crossover
distortion but has no effect on the input stage transition
distortion. For lowest distortion, the LT1783 should be
operated single supply, with the output always sourcing
current and with the input voltage swing between ground
and (V
istics curves, “Total Harmonic Distortion + Noise vs Out-
put Voltage Amplitude.”
Gain
The open-loop gain is almost independent of load when
the output is sourcing current. This optimizes perfor-
mance in single supply applications where the load is
returned to ground. The typical performance curve of
open-loop gain for various loads shows the details.
Shutdown
The 6-lead part includes a shutdown feature that disables
the part, reducing quiescent current and making the
output high impedance. The part can be shut down by
bringing the SHDN pin 1.2V or more above V
down, the supply current is about 5 A and the output
leakage current is less than 1 A (V
normal operation, the SHDN pin can be tied to V
floating. See the Typical Performance Characteristics
curves, “Supply Current vs Shutdown Voltage.”
+
– 0.8V). See the Typical Performance Character-
+
), the CMRR is very good,
–
V
OUT
–
LT1783
. When shut
–
V
or left
+
). In
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