LOG112 Datasheet, PDF (3/16 Pages) Texas Instruments – LOGARITHMIC AND LOG RATIO AMPLIFIERS

ELECTRICAL CHARACTERISTICS
Boldface limits apply over the specified temperature range, T_A = –5°C to +75°C.
At T_A = +25°C, V_S = ±5V, and R_OUT = 10kΩ, unless otherwise noted.
LOG112, LOG2112
PARAMETER
CONDITION
MIN
TYP
MAX
UNITS
CORE LOG FUNCTION
V_IN / V_OUT Equation
LOG CONFORMITY ERROR⁽¹⁾
Initial
over Temperature
GAIN⁽²⁾
Initial Value
Gain Error
vs Temperature
INPUT, A_1A and A_1B, A_2A, A_2B
Offset Voltage
vs Temperature
vs Power Supply (PSRR)
Input Bias Current
vs Temperature
Voltage Noise
Current Noise
Common-Mode Voltage Range (Positive)
(Negative)
Common-Mode Rejection Ratio (CMRR)
OUTPUT, (V_{LOG OUT}) A_2A, A_2B
Output Offset, V_OSO, Initial
vs Temperature
Full-Scale Output (FSO)
Short-Circuit Current
TOTAL ERROR⁽³⁾⁽⁴⁾
Initial
vs Temperature
vs Supply
1nA to 100µA (5 decades)
100pA to 3.5mA (7.5 decades)
1nA to 100µA (5 decades)
100pA to 3.5mA (7.5 decades)
1nA to 100µA
1nA to 100µA
T_MIN to T_MAX
T_MIN to T_MAX
V_S = ±4.5V to ±18V
T_MIN to T_MAX
f = 10Hz to 10kHz
f = 1kHz
f = 1kHz
T_MIN to T_MAX
V_S = ±5V
I₁ or I₂ remains fixed while other varies.
Min to Max
I₁ or I₂ = 5mA (V_S ≥ ±6V)
I₁ or I₂ = 3.5mA
I₁ or I₂ = 1mA
I₁ or I₂ = 100µA
I₁ or I₂ = 10µA
I₁ or I₂ = 1µA
I₁ or I₂ = 100nA
I₁ or I₂ = 10nA
I₁ or I₂ = 1nA
I₁ or I₂ = 350pA
I₁ or I₂ = 100pA
I₁ or I₂ = 3.5mA
I₁ or I₂ = 1mA
I₁ or I₂ = 100µA
I₁ or I₂ = 10µA
I₁ or I₂ = 1µA
I₁ or I₂ = 100nA
I₁ or I₂ = 10nA
I₁ or I₂ = 1nA
I₁ or I₂ = 350pA
I₁ or I₂ = 100pA
I₁ or I₂ = 3.5mA
I₁ or I₂ = 1mA
I₁ or I₂ = 100µA
I₁ or I₂ = 10µA
I₁ or I₂ = 1µA
I₁ or I₂ = 100nA
I₁ or I₂ = 10nA
I₁ or I₂ = 1nA
I₁ or I₂ = 350pA
I₁ or I₂ = 100pA
V_LOGOUT = (0.5V)LOG (I₁/I₂)
0.01
0.2
0.13
0.0001
0.005
0.5
0.10
±1
0.003
0.01
±0.3
±1.5
±2
5
20
±5
Doubles Every 10°C
3
30
4
(V+) – 2
(V+) – 1.5
(V–) + 2
(V–) + 1.2
10
±3
±15
±10
(V–) + 1.2
(V+) – 1.5
±18
±1.2
±0.4
±0.1
±0.05
±0.05
±0.09
±0.2
±0.3
±0.1
±0.3
±3.0
±0.1
±0.1
±0.1
±0.1
±0.1
±0.1
±0.25
±0.1
±0.1
±150
±75
±20
±20
±20
±20
±20
±20
±20
±20
±20
V
%
%
% / °C
% / °C
V/decade
%
% / °C
mV
µV/°C
µV/V
pA
µVrms
nV/√Hz
fA/√Hz
V
V
µV/V
mV
µV/°C
V
mA
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ °C
mV/ V
mV/ V
mV/ V
mV/ V
mV/ V
mV/ V
mV/ V
mV/V
mV/ V
mV/ V
NOTES: (1) Log Conformity Error is the peak deviation from the best-fit-straight line of V_O 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.
LOG112, 2112
3
SBOS246C
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