lt1801is8-trpbf Linear Technology Corporation, lt1801is8-trpbf Datasheet - Page 17

• 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

TYPICAL APPLICATIO S
Single Supply 1A Laser Driver Amplifier
Figure 4 shows the LT1801 used in a 1A laser driver
application. One of the reasons the LT1801 is well suited
to this control task is that its 2.3V operation ensures that
it will be awaked during power-up and operated before the
circuit can otherwise cause significant current to flow in
the 2.1V threshold laser diode. Driving the noninverting
input of the LT1801 to a voltage V
on of the high current NPN transistor, FMMT619 and the
laser diode. A current equal to V
laser diode. The LT1801 low offset voltage and low input
IN
IN
U
100mA/DIV
/R1 flows through the
will control the turning
DO NOT FLOAT
Figure 4. Single Supply 1A Laser Driver Amplifier
V
IN
Figure 5. 500mA Pulse Response
+
–
1/2 LT1801
50ns/DIV
bias current allows it to control the current that flows
through the laser diode precisely. The overall circuit is a 1A
per volt V-to-I converter. Frequency compensation com-
ponents R2 and C1 are selected for fast but zero-over-
shoot time domain response to avoid overcurrent condi-
tions in the laser. The time domain response of this circuit,
measured at R1 and given a 500mV 230ns input pulse, is
shown in Figure 5. While the circuit is capable of 1A
operation, the laser diode and the transistor are thermally
limited due to power dissipation, so they must be operated
at low duty cycles.
C1
39pF
10 Ω
330 Ω
R3
R2
5V
18012 F05
Q1
ZETEX
FMMT619
R1
1 Ω
18012 F04
IR LASER
INFINEON
SFH495
LT1801/LT1802
17
18012fb