LOG112 Datasheet, PDF (5/16 Pages) Texas Instruments – LOGARITHMIC AND LOG RATIO AMPLIFIERS

TYPICAL CHARACTERISTICS
At T_A = +25°C, V_S = ±5V, and R_L = 10kΩ, unless otherwise noted.
NORMALIZED TRANSFER FUNCTION
2.0
V_LOGOUT = (0.5V)LOG (I₁/I₂)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
0.0001 0.001 0.01 0.1 1 10 100 1k 10k
Current Ratio, I₁/I₂
ONE CYCLE OF NORMALIZED TRANSFER FUNCTION
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
1
10
Current Ratio, I₁/I₂
TOTAL ERROR (–5°C)
20
15
10
5
0
–5
–10
–15
10 to 15
–20
5 to 10
0 to 5
–5 to 0
I₁
I₂
20
15
10
5
0
–5
–10
–15
–20
TOTAL ERROR (25°C)
20
20
15
15
10
10
5
5
0
–5
0
–10
–5
–15
–10
–20
5 to 10
–15
0 to 5
–20
–5 to 0
I₁
I₂
TOTAL ERROR (70°C)
100
100
80 to 100
80
60 to 80
80
60
40 to 60
20 to 40
60
40
0 to 20
–20 to 0
40
20
20
0
0
–20
–20
I₁
I₂
8
7
6
5
4
3
2
1
0
–1
–2
100pA 1nA
GAIN ERROR (I₂ = 1µA)
+85°C
+75°C
–40°C
–5°C +25°C
10nA 100nA 1µA 10µA 100µA 1mA 10mA
Input Current (I₁ or I₂)
LOG112, 2112
5
SBOS246C
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