lt1801is8-trpbf Linear Technology Corporation, lt1801is8-trpbf Datasheet - Page 15

• Manufacturer Part Number: lt1801is8-trpbf
• Description: Lt1802 - Quad 80mhz, 25v/?s Low Power Rail-to-rail Input And Output Precision Op Amps
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
voltage is at half of either supply voltage (or the maximum
swing is less than 1/2 supply voltage). P
Example: An LT1801 in an SO-8 package operating on ±5V
supplies and driving a 50Ω load, the worst-case power
dissipation is given by:
If both amplifiers are loaded simultaneously, then the total
power dissipation is 0.34W.
The maximum ambient temperature that the part is al-
lowed to operate is:
Input Offset Voltage
The offset voltage will change depending upon which input
stage is active. The PNP input stage is active from the
negative supply rail to 1.2V from the positive supply rail,
then the NPN input stage is activated for the remaining input
range up to the positive supply rail during which the PNP
stage remains inactive. The offset voltage is typically less
than 75µV in the range that the PNP input stage is active.
Input Bias Current
The LT1801/LT1802 employ a patent-pending technique
to trim the input bias current to less than 250nA for the
input common mode voltage of 0.2V above negative
supply rail to 1.2V of the positive rail. The low input offset
voltage and low input bias current of the LT1801/LT1802
provide precision performance especially for high source
impedance applications.
P
P
T
A
DMAX
DMAX
= T
= 150°C – (0.34W • 190°C/W) = 85°C
J
= (V
= (10 • 4.5mA) + (2.5)
= 0.17W
– (P
S
DMAX
• I
SMAX
U
• 190°C/W)
) + (V
U
S
/2)
2
2
/50 = 0.045 + 0.125
/R
W
L
DMAX
is given by:
U
Output
The LT1801/LT1802 can deliver a large output current, so
the short-circuit current limit is set around 50mA to
prevent damage to the device. Attention must be paid to
keep the junction temperature of the IC below the absolute
maximum rating of 150°C (refer to the Power Dissipation
section) when the output is continuously short circuited.
The output of the amplifier has reverse-biased diodes
connected to each supply. If the output is forced beyond
either supply, unlimited current will flow through these
diodes. If the current is transient and limited to several
hundred mA and the total supply voltage is less than
12.6V, the absolute maximum rating, no damage will
occur to the device.
Overdrive Protection
When the input voltage exceeds the power supplies, two
pairs of crossing diodes D1 to D4 will prevent the output
from reversing polarity. If the input voltage exceeds either
power supply by 700mV, diode D1/D2 or D3/D4 will turn
on to keep the output at the proper polarity. For the phase
reversal protection to perform properly, the input current
must be limited to less than 10mA. If the amplifier is
severely overdriven, an external resistor should be used to
limit the overdrive current.
The LT1801/LT1802’s input stages are also protected
against a large differential input voltage of 1.4V or higher
by a pair of back-back diodes D5/D8 to prevent the emitter-
base breakdown of the input transistors. The current in these
diodes should be limited to less than 10mA when they are
active. The worst-case differential input voltage usually
occurs when the input is driven while the output is shorted
to ground in a unity gain configuration. In addition, the
amplifier is protected against ESD strikes up to 3kV on all
pins by a pair of protection diodes on each pin that are
connected to the power supplies as shown in Figure 1.
LT1801/LT1802
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