LT1638HS8 Linear Technology, LT1638HS8 Datasheet - Page 12

• Manufacturer Part Number: LT1638HS8
• Description: IC OPAMP R-R IN/OUT DUAL 8-SOIC
• Manufacturer: Linear Technology
• Series: Over-The-Top®r

Specifications of LT1638HS8

• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 0.4 V/µs
• Gain Bandwidth Product: 1.2MHz
• Current - Input Bias: 20nA
• Voltage - Input Offset: 250µV
• Current - Supply: 205µA
• Current - Output / Channel: 40mA
• Voltage - Supply, Single/dual (±): 2.5 V ~ 44 V, ±1.25 V ~ 22 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• -3db Bandwidth: -

LT1638/LT1639
APPLICATIONS INFORMATION
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
good, typically 98dB. When the LT1638 switches between
input stages there is signifi cant 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 LT1638/LT1639 should
be operated single supply, with the output always sourcing
TYPICAL APPLICATIONS
With 1.2MHz bandwidth, Over-The-Top capability, reverse-
battery protection and rail-to-rail input and output features,
the LT1638/LT1639 are ideal candidates for general purpose
applications.
The lowpass slope limiting fi lter in Figure 1 limits the
maximum dV/dT (not frequency) that it passes. When the
input signal differs from the output by one forward diode
drop, D1 or D2 will turn on. With a diode on, the voltage
across R2 will be constant and a fi xed current, V
will fl ow through capacitor C1, charging it linearly instead
of exponentially. The maximum slope that the circuit will
pass is equal to V
how fast the input changes the output will never change
any faster than the dV/dT set by the diodes and (R2)(C).
A modifi cation of this application is shown in Figure 2 using
references instead of diodes to set the maximum slope. By
using references, the slope is independent of temperature.
A scope photo shows a 1V
pulse added to the sine wave; the circuit passes the 2kHz
signal but limits the slope of the pulse.
12
dt
dt
d
FOR R1 = 10k, R2 = 100k, C1 = 1000pF
d
V
V
OUT(MAX)
OUT(MAX)
=
= 0.006V/μs
Figure 1. Lowpass Slope Limiting Filter
(R2)(C1)
V
D
V
IN
DIODE
R1
divided by (R2)(C1). No matter
P-P
R2
, 2kHz input signal with a 2V
C1
+
–
+
1/2 LT1638
), the CMRR is very
D1
D2
DIODE
1638/39 F01
V
/R2,
OUT
current and with the input voltage swing between ground
and (V
istics curves.
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.
dt
V
FOR R2 = 50k, C1 = 500pF ,
MAXIMUM SLOPE = 0.048V/μs
d
D1 TO D4 = IN4148
IN
V
OUT
+
Figure 2. Lowpass Slope Limiting Filter with 0 TC
V
=
OUT
R1
V
1k
– 0.8V). See the Typical Performance Character-
(R2)(C1)
IN
1.2V
Response of Slope Limiting Filter
D1
100k
D3
R2
R4
100k
R3
C1
D2
D4
–
+
1/4 LT1639
1/4 LT1639
1/4 LT1639
+
–
–
+
1638/39 TA02
V
V
CC
EE
R5
100k
R6
100k
LT1634-1.2V
LT1634-1.2V
V
1638/39 F02
OUT
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