TL03x, TL03xA
ENHANCED-JFET LOW-POWER LOW-OFFSET
OPERATIONAL AMPLIFIERS
SLOS180C – FEBRUARY 1997 – REVISED DECEMBER 2001
47
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
low-level light-detector preamplifier
Applications that need to detect small currents require high input-impedance operational amplifiers; otherwise,
the bias currents of the operational amplifier camouflage the current being monitored. Phototransistors provide
a current that is proportional to the light reaching the transistor. The TL03x allows even the small currents
resulting from low-level light to be detected.
In Figure 68, if there is no light, the phototransistor is off and the output is high. As light is detected, the
operational amplifier output begins pulling low. Adjusting R4 both compensates for offset voltage of the amplifier
and adjusts the point of light detection by the amplifier.
TL03x
–
+
R6
10 kΩ
C1
100 pF
R7
R3
R1
TIL601
R2 5 kΩ
R5
R4
10 kΩ
10 kΩ
10 kΩ
10 kΩ
10 kΩ
15 V
V
O
–15 V
Figure 68. Low-Level Light-Detector Preamplifier
