Datasheet

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LOG104
4
SBOS243C
TYPICAL CHARACTERISTICS
At T
A
= +25°C, V
S
= ±5V, R
L
= 10kΩ, unless otherwise noted.
ONE CYCLE OF NORMALIZED TRANSFER FUNCTION
Normalized Output Voltage (V)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
261103
Current Ratio, I
1
/I
2
48
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
Normalized Output Voltage (V)
NORMALIZED TRANSFER FUNCTION
0.0001 0.001 0.01 0.1 1 10 100 1k
10k
Current Ratio, I
1
/I
2
V
OUT
= 0.5V LOG (I
1
/I
2
)
3dB FREQUENCY RESPONSE
3dB Frequency Response (Hz)
0.1
1M
100k
10k
1k
100
10
1
100µA
100µA
1mA
I
1
= 1mA
1µA
1mA
to 10µA
100nA
10nA
I
1
= 1nA
10nA
C
C
= 1000pF
C
C
= 1
µF
10
µA to 1
µA
C
C
= 10pF
1nA
100µA
100pA 1nA 10nA 100nA 1µA10µA 100µA1mA
I
2
1µA
10µA
100µA
I
1
= 1nA
10nA
120
100
80
60
40
20
0
100pA 1nA 10nA 100nA 1µA10µA 100µA 1mA 10mA
TOTAL ERROR vs INPUT CURRENT
Input Current (I
1
or I
2
)
Total Error (mV)
+75°C
+25°C –5°C
5.8
4.8
3.8
2.8
1.8
0.8
–0.2
100pA 1nA 10nA 100nA 1µA10µA 100µA 1mA 10mA
GAIN ERROR (I
2
= 1µA)
Input Current (I
1
or I
2
)
Gain Error (%)
–5°C to –40°C
+85°C
+75°C
+25°C
MINIMUM VALUE OF COMPENSATION CAPACITOR
100M
10M
1M
100k
10k
1k
100
10
1
C
C
(pF)
100pA 1nA 10nA 100nA 1µA10µA 100µA 1mA 10mA
I
2
I
1
= 100pA
I
1
= 1nA
I
1
= 10nA
I
1
= 100nA
1µA
I
1
= 10µA
100µA
1mA
Select C
C
for I
1
min.
and I
2
max. Values
below 2pF may be ignored.