LT1398/LT1399/LT1399HV
PIN FUNCTIONS
LT1398
– IN A (Pin 1):
Inverting Input of A Channel Amplifier.
+ IN A (Pin 2):
Noninverting Input of A Channel Amplifier.
GND (Pins 3, 4, 5, 6):
Ground. Not connected internally.
+ IN B (Pin 7):
Noninverting Input of B Channel Amplifier.
– IN B (Pin 8):
Inverting Input of B Channel Amplifier.
EN B (Pin 9):
B Channel Enable Pin. Logic low to enable.
OUT B (Pin 10):
B Channel Output.
V
–
(Pin 11):
Negative Supply Voltage, Usually – 5V.
GND (Pins 12, 13):
Ground. Not connected internally.
V
+
(Pin 14):
Positive Supply Voltage, Usually 5V.
OUT A (Pin 15):
A Channel Output.
EN A (Pin 16):
A Channel Enable Pin. Logic low to enable.
APPLICATI
S I FOR ATIO
Feedback Resistor Selection
The small-signal bandwidth of the LT1398/LT1399/
LT1399HV is set by the external feedback resistors and the
internal junction capacitors. As a result, the bandwidth is
a function of the supply voltage, the value of the feedback
resistor, the closed-loop gain and the load resistor. The
LT1398/LT1399 have been optimized for
±5V
supply
operation and have a – 3dB bandwidth of 300MHz at a gain
of 2. The LT1399HV provides performance similar to the
LT1399. Please refer to the resistor selection guide in the
Typical AC Performance table.
Capacitance on the Inverting Input
Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.
U
W
U
U
UO
U
U
LT1399, LT1399HV
– IN R (Pin 1):
Inverting Input of R Channel Amplifier.
+ IN R (Pin 2):
Noninverting Input of R Channel Amplifier.
GND (Pin 3):
Ground. Not connected internally.
– IN G (Pin 4):
Inverting Input of G Channel Amplifier.
+ IN G (Pin 5):
Noninverting Input of G Channel Amplifier.
GND (Pin 6):
Ground. Not connected internally.
+ IN B (Pin 7):
Noninverting Input of B Channel Amplifier.
– IN B (Pin 8):
Inverting Input of B Channel Amplifier.
EN B (Pin 9):
B Channel Enable Pin. Logic low to enable.
OUT B (Pin 10):
B Channel Output.
V
–
(Pin 11):
Negative Supply Voltage, Usually – 5V.
OUT G (Pin 12):
G Channel Output.
EN G (Pin 13):
G Channel Enable Pin. Logic low to enable.
V
+
(Pin 14):
Positive Supply Voltage, Usually 5V.
OUT R (Pin 15):
R Channel Output.
EN R (Pin 16):
R Channel Enable Pin. Logic low to enable.
Take care to minimize the stray capacitance between the
output and the inverting input. Capacitance on the invert-
ing input to ground will cause peaking in the frequency
response (and overshoot in the transient response).
Capacitive Loads
The LT1398/LT1399/LT1399HV can drive many capaci-
tive loads directly when the proper value of feedback
resistor is used. The required value for the feedback
resistor will increase as load capacitance increases and as
closed-loop gain decreases. Alternatively, a small resistor
(5Ω to 35Ω) can be put in series with the output to isolate
the capacitive load from the amplifier output. This has the
advantage that the amplifier bandwidth is only reduced
when the capacitive load is present. The disadvantage is
that the gain is a function of the load resistance.
9
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