R

REF

15V

3.6k

I

REF

–15V

6V

I

REF = 6V / RREF

Figure 7-3. Temperature-Compensated Current Source

7.1.4 Negative Input Currents

The LOG114 functions only with positive input currents (conventional current flows into input current pins). In

situations where negative input currents are needed, the example circuits in Figure 7-4, Figure 7-5, and Figure

7-6 can be referenced.

TLV9101

–

+

D

2

D

1

I

REF

I

OUT

Figure 7-4. Current Inverter/Current Source

1k

3.3V

10nA to 1mA

1.5k

LOG114

10nA to 1mA

Pin 3 or Pin 4

OPA2383

–

+

OPA2383

–

+

Figure 7-5. Precision Current Inverter/Current Source

100k

100k

100k

100k

1k

3.3V

10nA to 1mA

1.5k

3.3V

1.5k

LOG114

10nA to 1mA

Pin 3 or Pin 4

OPA2383

–

+

OPA2383

–

+

Figure 7-6. Precision Current Inverter/Current Source

7.1.5 Voltage Inputs

The LOG114 was optimized for current inputs. Voltage inputs may be handled directly by using a low-impedance

voltage source with series resistors, but the dynamic input range is limited to approximately three decades

LOG114

SBOS301B – MAY 2004 – REVISED MARCH 2025

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