Datasheet

www.ti.com
LOG102
4
SBOS211B
TYPICAL CHARACTERISTICS
At T
A
= +25°C, V
S
= ±5V, R
L
= 10kΩ, unless otherwise noted.
0
ONE CYCLE OF NORMALIZED TRANSFER FUNCTION
Normalized Output Voltage (V)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
261103
Current Ratio,
I
1
I
2
48
3dB FREQUENCY RESPONSE
I
2
3dB Frequency Response (Hz)
0.1
1nA
1M
100k
10k
1k
100
10
1
10nA 100nA 1µA10µA 100µA 1mA
100µA
100µA
1mA
I
1
= 1mA
1µA
1mA
to 10µA
100nA
10nA
I
1
= 1nA
10nA
10nA
1µA
10µA
100µA
C
C
=
1
µ
F
C
C
= 1000pF
10
µ
A
to 1
µ
A
C
C
= 10pF
I
1
= 1nA
1nA
100µA
NORMALIZED TRANSFER FUNCTION
Normalized Output Voltage (V)
0.001
3
2
1
0
–1
–2
–3
0.01 1 100
Current Ratio,
0.1 10 1000
I
1
I
2
I
1
I
2
V
OUT
= 1V • Log
TOTAL ERROR vs INPUT CURRENT
Total Error (mV)
1nA
60
50
40
30
20
10
0
100nA10nA
70°C
0°C
25°C
10µA 100µA
Input Current
(I
1
or I
2
)
1µA 1mA
MINIMUM VALUE OF COMPENSATION CAPACITOR
C
C
(pF)
1nA
10000
1000
100
10
1
100nA10nA 10µA 1mA
I
2
1µA 100µA 10mA
Select C
C
for I
1
min
and I
2
max
I
1
= 1nA
Values below 2pF
may be ignored.
I
1
= 1mA
I
1
= 100µA
I
1
= 10nA
I
1
= 100nA
I
1
= 1µA
I
1
= 10µA
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
–0.05
–0.10
–60 –40 –20 0 20 40 60 80
GAIN ERROR vs TEMPERATURE
Gain Error (%)
Temperature (°C)