LOG112, 2112
3
SBOS246D
www.ti.com
ELECTRICAL CHARACTERISTICS
Boldface limits apply over the specified temperature range, TA = –5°C to +75°C.
At TA = +25°C, VS = ±5V, and ROUT = 10k, unless otherwise noted.
LOG112, LOG2112
PARAMETER
CONDITION
MIN
TYP
MAX
UNITS
CORE LOG FUNCTION
VIN /VOUT Equation
VLOGOUT = (0.5V)LOG (I1/I2)V
LOG CONFORMITY ERROR(1)
Initial
1nA to 100
A (5 decades)
0.01
0.2
%
100pA to 3.5mA (7.5 decades)
0.13
%
over Temperature
1nA to 100
A (5 decades)
0.0001
%/
°C
100pA to 3.5mA (7.5 decades)
0.005
%/
°C
GAIN(2)
Initial Value
1nA to 100
A
0.5
V/decade
Gain Error
1nA to 100
A
0.10
±1%
vs Temperature
TMIN to TMAX
0.003
0.01
%/
°C
INPUT, A1A and A1B, A2A, A2B
Offset Voltage
±0.3
±1.5
mV
vs Temperature
TMIN to TMAX
±2
V/
°C
vs Power Supply (PSRR)
VS = ±4.5V to ±18V
5
20
V/V
Input Bias Current
±5pA
vs Temperature
TMIN to TMAX
Doubles Every 10
°C
Voltage Noise
f = 10Hz to 10kHz
3
Vrms
f = 1kHz
30
nV/
√Hz
Current Noise
f = 1kHz
4
fA/
√Hz
Common-Mode Voltage Range (Positive)
(V+) – 2
(V+) – 1.5
V
(Negative)
(V–) + 2
(V–) + 1.2
V
Common-Mode Rejection Ratio (CMRR)
10
V/V
OUTPUT, (VLOG OUT) A2A, A2B
Output Offset, VOSO, Initial
±3
±15
mV
vs Temperature
TMIN to TMAX
±10
V/°C
Full-Scale Output (FSO)
VS = ±5V
(V–) + 1.2
(V+) – 1.5
V
Short-Circuit Current
±18
mA
TOTAL ERROR(3)(4)
I1 or I2 remains fixed while other varies.
Initial
Min to Max
I1 or I2 = 5mA (VS ≥ ±6V)
±150
mV
I1 or I2 = 3.5mA
±75
mV
I1 or I2 = 1mA
±20
mV
I1 or I2 = 100A
±20
mV
I1 or I2 = 10A
±20
mV
I1 or I2 = 1A
±20
mV
I1 or I2 = 100nA
±20
mV
I1 or I2 = 10nA
±20
mV
I1 or I2 = 1nA
±20
mV
I1 or I2 = 350pA
±20
mV
I1 or I2 = 100pA
±20
mV
vs Temperature
I1 or I2 = 3.5mA
±1.2
mV/
°C
I1 or I2 = 1mA
±0.4
mV/
°C
I1 or I2 = 100A
±0.1
mV/
°C
I1 or I2 = 10A
±0.05
mV/
°C
I1 or I2 = 1A
±0.05
mV/
°C
I1 or I2 = 100nA
±0.09
mV/
°C
I1 or I2 = 10nA
±0.2
mV/
°C
I1 or I2 = 1nA
±0.3
mV/
°C
I1 or I2 = 350pA
±0.1
mV/
°C
I1 or I2 = 100pA
±0.3
mV/
°C
vs Supply
I1 or I2 = 3.5mA
±3.0
mV/ V
I1 or I2 = 1mA
±0.1
mV/ V
I1 or I2 = 100A
±0.1
mV/ V
I1 or I2 = 10A
±0.1
mV/ V
I1 or I2 = 1A
±0.1
mV/ V
I1 or I2 = 100nA
±0.1
mV/ V
I1 or I2 = 10nA
±0.1
mV/ V
I1 or I2 = 1nA
±0.25
mV/V
I1 or I2 = 350pA
±0.1
mV/ V
I1 or I2 = 100pA
±0.1
mV/ V
NOTES: (1) Log Conformity Error is the peak deviation from the best-fit-straight line of VO versus LOG (I1/I2) curve expressed as a percent of peak-to-peak full-
scale output. K, scale factor, equals 0.5V output per decade of input current. (2) Scale factor of core log function is trimmed to 0.5V output per decade change of
input current. (3) Worst-case Total Error for any ratio of I1/I2, as the largest of the two errors, when I1 and I2 are considered separately. (4) Total Error includes offset
voltage, bias current, gain, and log conformity. (5) Bandwidth (3dB) and transient response are a function of both the compensation capacitor and the level of input
current.