Datasheet

LT1806/LT1807
19
18067fc
APPLICATIONS INFORMATION
The maximum ambient temperature that the part is
allowed to operate is:
T
A
= T
J
– (P
D(MAX)
• 105°C/W)
= 150°C – (0.53W • 105°C/W) = 94°C
To operate the device at higher ambient temperature,
connect more metal area to the V
–
pin to reduce the thermal
resistance of the package as indicated in Table 2.
Input Offset Voltage
The offset voltage will change depending upon which
input stage is active and the maximum offset voltage is
guaranteed to less than 550μV. To maintain the precision
characteristics of the amplifi er, the change of V
OS
over the
entire input common mode range (CMRR) is limited to be
less than 550μV on a single 5V and 3V supply.
Input Bias Current
The input bias current polarity depends on a given input
common voltage at which the input stage is operating.
When the PNP input stage is active, the input bias currents
fl ow out of the input pins. When the NPN input stage is
activated, the input bias current fl ows into the input pins.
Because the input offset current is less than the input bias
current, matching the source resistances at the input pins
will reduce total offset error.
Output
The LT1806/LT1807 can deliver a large output current, so
the short-circuit current limit is set around 85mA 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 amplifi er has reverse-biased diodes connected to
each supply. If the output is forced beyond either supply,
unlimited current will fl ow through these diodes. If the
current is transient and limited to one hundred milliamps
or less, no damage to the device will occur.
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 5mA. If the amplifi er is severely
overdriven, an external resistor should be used to limit
the overdrive current.