LOG114 Datasheet, PDF (17/30 Pages) Burr-Brown (TI) – Single-Supply, High-Speed, Precision LOGARITHMIC AMPLIFIER

LOG114
www.ti.com
NEGATIVE INPUT CURRENTS
The LOG114 functions only with positive input currents
(conventional current flows into input current pins). In
SBOS301A − MAY 2004 − REVISED MARCH 2007
situations where negative input currents are needed,
the example circuits in Figure 7, Figure 8, and Figure 9
may be used.
I_IN
Q_A
D₁
Q_B
National
LM394
D₂
OPA 70 3
Figure 7. Current Inverter/Current Source.
+3.3V
+5V
1/2
OPA2335
1kΩ
(+3.3V
10nA to 1mA Back Bias)
Photodiode
I_OUT
1.5kΩ
+5V
1/2
OPA2335
BSH203
LOG114
10nA to 1mA
Pin 3 or Pin 4
Figure 8. Precision Current Inverter/Current Source.
10nA to 1mA
+3.3V
Back Bias
+3.3V
Photodiode
1kΩ
+5V
1/2
OPA2335
Figure 9. Precision Current Inverter/Current Source.
100kΩ
100kΩ
+5V
1/2
OPA2335
1.5kΩ
1.5kΩ
100kΩ
100kΩ
10nA to 1mA
Pin 3 or Pin 4
LOG114
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