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产品型号LOG101AID的概述

LOG101AID芯片概述 LOG101AID是一款由Texas Instruments（德州仪器）公司研发的高性能模拟信号处理芯片，专门用于信号的对数转换。该芯片广泛应用于音频设备、传感器接口以及其它需要将非线性信号转换为线性信号的领域。由于其出色的动态范围和精度，LOG101AID成为了电子工程师在设计系统时的常用组件之一。 LOG101AID采用对数放大器结构，能够将输入信号进行对数压缩，使得在信号处理过程中可以更加高效地使用动态范围。这种特性使得LOG101AID在许多高灵敏度应用场合中显得尤为重要。例如，在光电传感器领域，LOG101AID能够有效提升传感器的输出信号质量，从而提高测量精度。详细参数 LOG101AID的主要参数包括： - 输入信号范围：LOG101AID支持宽范围的输入信号，通常从微伏级别到几伏特，能够满足多种应用的需求。 - 转换时间：LOG101AID...

产品型号LOG101AID的Datasheet PDF文件预览

LOG101

SBOS242B – MAY 2002 – REVISED JUNE 2004

Precision

LOGARITHMIC AND LOG RATIO AMPLIFIER

DESCRIPTION

FEATURES

The LOG101 is a versatile integrated circuit that computes

the logarithm or log ratio of an input current relative to a

reference current.

●

EASY-TO-USE COMPLETE CORE FUNCTION

● HIGH ACCURACY: 0.01% FSO Over 5 Decades

● WIDE INPUT DYNAMIC RANGE:

The LOG101 is tested over a wide dynamic range of input

signals. In log ratio applications, a signal current can come

from a photodiode, and a reference current from a resistor in

series with a precision external reference.

7.5 Decades, 100pA to 3.5mA

● LOW QUIESCENT CURRENT: 1mA

● WIDE SUPPLY RANGE: ±4.5V to ±18V

The output signal at V_OUTis trimmed to 1V per decade of input

current allowing seven decades of input current dynamic

range.

APPLICATIONS

● LOG, LOG RATIO COMPUTATION:

Communication, Analytical, Medical, Industrial,

Test, and General Instrumentation

Low DC offset voltage and temperature drift allow accurate

measurement of low-level signals over a wide environmental

temperature range. The LOG101 is specified over the tem-

perature range –5°C to +75°C, with operation over

–40°C to +85°C.

● PHOTODIODE SIGNAL COMPRESSION AMPS

● ANALOG SIGNAL COMPRESSION IN FRONT

Note: Protected under US Patent #6,667,650; other patents pending.

OF ANALOG-TO-DIGITAL (A/D) CONVERTERS

I₂

C_C

V_OUT= (1V) • LOG (I₁/I₂)

V+

I₁

LOG101

Q₁

Q₂

A₂

A₁

V_OUT

R₂

R₁

GND

V–

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

www.ti.com

ABSOLUTE MAXIMUM RATINGS⁽¹⁾

Supply Voltage, V+ to V–.................................................................... 36V

ELECTROSTATIC

DISCHARGE SENSITIVITY

Input Voltage .................................................... (V–) – 0.5 to (V+) + 0.5V

Input Current ................................................................................... ±10mA

This integrated circuit can be damaged by ESD. Texas Instru-

ments recommends that all integrated circuits be handled with

appropriate precautions. Failure to observe proper handling

and installation procedures can cause damage.

Output Short-Circuit⁽²⁾.............................................................. Continuous

Operating Temperature ....................................................–40°C to +85°C

Storage Temperature .....................................................–55°C to +125°C

Junction Temperature .................................................................... +150°C

Lead Temperature (soldering, 10s) ............................................... +300°C

ESD damage can range from subtle performance degrada-

tion to complete device failure. Precision integrated circuits

may be more susceptible to damage because very small

parametric changes could cause the device not to meet its

published specifications.

NOTES: (1) Stresses above these ratings may cause permanent damage.

Exposure to absolute maximum conditions for extended periods may degrade

device reliability. (2) Short-circuit to ground.

PIN DESCRIPTION

Top View

I₁

I₂

GND

V–

LOG101

V_OUT

V+

NC = No Internal Connection

PACKAGE/ORDERING INFORMATION⁽¹⁾

SPECIFIED

PACKAGE

DESIGNATOR

TEMPERATURE

RANGE

PACKAGE

MARKING

ORDERING

NUMBER

TRANSPORT

MEDIA, QUANTITY

PRODUCT

PACKAGE-LEAD

LOG101AID

SO-8

–5°C to +75°C

LOG101

LOG101AID

Rails, 100

LOG101AIDR

Tape and Reel, 2500

NOTE: (1) For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet.

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.

LOG101AID

PARAMETER

CONDITION

MIN

TYP

MAX

UNITS

CORE LOG FUNCTION

_IN/V_OUTEquation

V_O= (1V) • log (I₁/I₂)

LOG CONFORMITY ERROR⁽¹⁾

Initial

1nA to 100µA (5 decades)

100pA to 3.5mA (7.5 decades)

1nA to 100µA (5 decades)

0.01

0.06

0.0001

0.0005

0.2

%/°C

over Temperature

100pA to 3.5mA (7.5 decades)⁽²⁾

GAIN⁽³⁾

Initial Value

Gain Error

vs Temperature

1nA to 100µA

T_MINto T_MAX

V/decade

%/°C

0.15

0.003

±1

0.01

INPUT, A1 and A2

Offset Voltage

±0.3

±2

±5

±1.5

µV/°C

µV/V

vs Temperature

vs Power Supply (PSRR)

Input Bias Current

vs Temperature

Voltage Noise

T_MINto T_MAX

V_S= ±4.5V to ±18V

T_MINto T_MAX

f = 10Hz to 10kHz

f = 1kHz

Doubles Every 10°C

µVrms

nV/√Hz

fA/√Hz

Current Noise

Common-Mode Voltage Range (Positive)

(Negative)

f = 1kHz

(V+) – 2

(V–) + 2

(V+) – 1.5

(V–) + 1.2

105

Common-Mode Rejection Ratio (CMRR)

OUTPUT, A2 (V_OUT

)

Output Offset, V_OSO, Initial

vs Temperature

Full-Scale Output (FSO)

Short-Circuit Current

±3

±2

±15

µV/°C

T_MINto T_MAX

V_S= ±5V

(V–) + 1.2

(V+) – 1.5

±18

LOG101

www.ti.com

SBOS242B

ELECTRICAL CHARACTERISTICS (Cont.)

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_L= 10kΩ, unless otherwise noted.

LOG101AID

PARAMETER

CONDITION

MIN

TYP

MAX

UNITS

TOTAL ERROR⁽⁴⁾⁽⁵⁾

Initial

I₁or I₂remains fixed while other varies.

Min to Max

I₁or I₂= 3.5mA

I₁or I₂= 1mA

I₁or I₂= 100µA

I₁or I₂= 10µA

I₁or I₂= 1µA

I₁or I₂= 100nA

I₁or I₂= 10nA

I₁or I₂= 1nA

I₁or I₂= 350pA

I₁or I₂= 100pA

I₁or I₂= 3.5mA

I₁or I₂= 1mA

I₁or I₂= 100µA

I₁or I₂= 10µA

I₁or I₂= 1µA

I₁or I₂= 100nA

I₁or I₂= 10nA

I₁or I₂= 1nA

I₁or I₂= 350pA

I₁or I₂= 100pA

I₁or I₂= 3.5mA

I₁or I₂= 1mA

I₁or I₂= 100µA

I₁or I₂= 10µA

I₁or I₂= 1µA

I₁or I₂= 100nA

I₁or I₂= 10nA

I₁or I₂= 1nA

±75

±20

vs Temperature

±1.2

±0.4

±0.1

±0.05

±0.09

±0.2

±0.3

±0.1

±0.3

±3.0

±0.1

±0.25

±0.1

mV/°C

mV/V

vs Supply

I₁or I₂= 350pA

I₁or I₂= 100pA

FREQUENCY RESPONSE, CORE LOG⁽⁶⁾

BW, 3dB

I₂= 10nA

I₂= 1µA

I₂= 10µA

I₂= 1mA

C_C= 4500pF

C_C= 150pF

C_C= 50pF

0.1

kHz

Step Response

Increasing

I₂= 1µA to 1mA

I₂= 100nA to 1µA

I₂= 10nA to 100nA

Decreasing

C_C= 150pF

110

µs

I₂= 1mA to 1µA

I₂= 1µA to 100nA

I₂= 100nA to 10nA

C_C= 150pF

550

µs

POWER SUPPLY

Operating Range

Quiescent Current

V_S

I_O= 0

±4.5

±18

±1.5

±1

TEMPERATURE RANGE

Specified Range, T_MINto T_MAX

Operating Range

–5

–40

–55

125

°C

Storage Range

Thermal Resistance, θ_JASO-8

150

°C/W

NOTES: (1) Log Conformity Error is peak deviation from the best-fit straight line of V_OUTversus log (I₁/I₂) curve expressed as a percent of peak-to-peak full-scale.

(2) May require higher supply for full dynamic range.

(3) Output core log function is trimmed to 1V output per decade change of input current.

(4) Worst-case Total Error for any ratio of I₁/I₂is the largest of the two errors, when I₁and I₂are considered separately.

(5) Total I₁+ I₂should be kept below 4.5mA on ±5V supply.

(6) Bandwidth (3dB) and transient response are a function of both the compensation capacitor and the level of input current.

LOG101

SBOS242B

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TYPICAL CHARACTERISTICS

At T_A= +25°C, V_S= ±5V, and R_L= 10kΩ, unless otherwise noted.

ONE CYCLE OF NORMALIZED TRANSFER FUNCTION

NORMALIZED TRANSFER FUNCTION

4.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

V_OUT= 1V LOG (I₁/I₂)

3.0

2.0

1.0

0.0

–1.0

–2.0

–3.0

–4.0

0.1

0.0001 0.001 0.01

0.1

100

10k

Current Ratio, I₁/I₂

GAIN ERROR (I₂= 1µA)

TOTAL ERROR vs INPUT CURRENT

120

100

5.8

4.8

+85°C

+75°C

+25°C

–5°C to –40°C

3.8

2.8

1.8

+25°C –5°C

0.8

–0.2

100pA 1nA 10nA 100nA 1µA 10µA 100µA 1mA 10mA

Input Current (I₁or I₂)

3dB FREQUENCY RESPONSE

MINIMUM VALUE OF COMPENSATION CAPACITOR

100M

Select C_Cfor I₁min.

and I₂max. Values

10µA

100µA

1mA

10M

100k

10k

100k

10k

1µA

below 2pF may be ignored.

I₁= 100pA

= 1mA

100µA

I₁= 1nA

I₁= 10nA

100µA

1µA

1nA

10nA

1mA

to 10µA

10nA

I₁= 100nA

100

100nA

10nA

I₁= 1nA

1µA

100

I = 1nA

I₁= 10µA

100µA

1mA

0.1

100pA 1nA 10nA 100nA 1µA

10µA 100µA 1mA

100pA 1nA 10nA 100nA 1µA 10µA 100µA 1mA 10mA

I₂

LOG101

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SBOS242B

TYPICAL CHARACTERISTICS (Cont.)

At T_A= +25°C, V_S= ±5V, and R_L= 10kΩ, unless otherwise noted.

LOG CONFORMITY vs INPUT CURRENT

LOG CONFORMITY vs TEMPERATURE

350

300

250

200

150

100

7 Decades

(100pA to 1mA)

+85°C

6 Decades

(1nA to 1mA)

+75°C

5 Decades

(1nA to 100µA)

–40°C to +25°C

–1

100pA

1nA 10nA 100nA 1µA

10µA 100µA 1mA

–40 –30 –20 –10

10 20 30 40 50 60 70 80 90

Input Current (I₁or I₂)

Temperature (°C)

INPUT CURRENT RANGE

APPLICATION INFORMATION

To maintain specified accuracy, the input current range of the

LOG101 should be limited from 100pA to 3.5mA. Input currents

outside of this range may compromise LOG101 performance.

Input currents larger than 3.5mA result in increased

nonlinearity. An absolute maximum input current rating of

10mA is included to prevent excessive power dissipation that

may damage the logging transistor.

The LOG101 is a true logarithmic amplifier that uses the

base-emitter voltage relationship of bipolar transistors to

compute the logarithm, or logarithmic ratio of a current ratio.

Figure 1 shows the basic connections required for operation

of the LOG101. In order to reduce the influence of lead

inductance of power-supply lines, it is recommended that

each supply be bypassed with a 10µF tantalum capacitor in

parallel with a 1000pF ceramic capacitor, as shown in

Figure 1. Connecting the capacitors as close to the LOG101

as possible will contribute to noise reduction as well.

On ±5V supplies, the total input current (I₁+ I₂) is limited to

4.5mA. Due to compliance issues internal to the LOG101, to

accommodate larger total input currents, supplies should be

increased.

Currents smaller than 100pA will result in increased errors due

to the input bias currents of op amps A₁and A₂(typically 5pA).

The input bias currents may be compensated for, as shown in

Figure 2. The input stages of the amplifiers have FET inputs,

with input bias current doubling every 10°C, which makes the

nulling technique shown practical only where the temperature

is fairly stable.

V+

10µF

1000pF

R₂

10kΩ

V–

V+

V_OUT

LOG101

R₁

1MΩ

V_OUT

I₁

LOG101

I₁

I₂

C_C

GND

R₁'

> 1MΩ

I₂

10µF

1000pF

V–

C_C

V–

R₂'

10kΩ

V+

FIGURE 1. Basic Connections of the LOG101.

FIGURE 2. Bias Current Nulling.

LOG101

SBOS242B

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SETTING THE REFERENCE CURRENT

V+

When the LOG101 is used to compute logarithms, either I₁or

I₂can be held constant and becomes the reference current to

which the other is compared.

I₁= 2.5nA to 1mA

2.5V

REF3025

V_OUT

1GΩ to 2.5kΩ

LOG101

100kΩ

100Ω

₂= 2.5nA

_OUTis expressed as:

10MΩ

V_OUT= (1V) • log (I₁/I₂)

(1)

+25mV

GND

I_REFcan be derived from an external current source (such as

shown in Figure 3), or it may be derived from a voltage

source with one or more resistors. When a single resistor is

used, the value may be large depending on I_REF. If I_REFis

10nA and +2.5V is used:

+2.5V

C_C

V–

OPA335 Chopper Op Amp

–2.5V

(2)

R_REF= 2.5V/10nA = 250MΩ

FIGURE 5. Current Source with Offset Compensation.

I_REF

2N2905

at different levels of input signals. Smaller input currents

require greater gains to maintain full dynamic range, and will

slow the frequency response of the LOG101.

R_REF

3.6kΩ

2N2905

+15V

–15V

IN834

FREQUENCY COMPENSATION

I_REF

R_REF

Frequency compensation for the LOG101 is obtained by

connecting a capacitor between pins 3 and 8. The size of the

capacitor is a function of the input currents, as shown in the

Typical Characteristic Curves (Minimum Value of Compen-

sation Capacitor). For any given application, the smallest

value of the capacitor which may be used is determined by

the maximum value of I₂and the minimum value of I₁. Larger

values of C_Cwill make the LOG101 more stable, but will

reduce the frequency response.

FIGURE 3. Temperature Compensated Current Source.

A voltage divider may be used to reduce the value of the

resistor, as shown in Figure 4. When using this method, one

must consider the possible errors caused by the amplifier’s

input offset voltage. The input offset voltage of amplifier A₁

has a maximum value of 1.5mV, making V_REFa suggested

value of 100mV.

In an application, highest overall bandwidth can be achieved

by detecting the signal level at V_OUT, then switching in

appropriate values of compensation capacitors.

V_REF= 100mV

R₁R₃

V_OS

–

+5V

NEGATIVE INPUT CURRENTS

A₁

I_REF

R₂

The LOG101 will function only with positive input currents

(conventional current flows into pins 1 and 8). In situations

where negative input currents are needed, the circuits in

Figures 6, 7, and 8 may be used.

R₃>> R₂

FIGURE 4. T Network for Reference Current.

Figure 5 shows a low-level current source using a series

resistor. The low offset op-amp reduces the effect of the

LOG101’s input offset voltage.

Q_A

Q_B

I_IN

National

LM394

FREQUENCY RESPONSE

The frequency response curve seen in the Typical Charac-

teristic Curves is shown for constant DC I₁and I₂with a small

signal AC current on one input.

D₁

D₂

The 3dB frequency response of the LOG101 is a function of

the magnitude of the input current levels and of the value of the

frequency compensation capacitor. See Typical Characteristic

Curve “3dB Frequency Response” for details.

OPA703

I_OUT

The transient response of the LOG101 is different for in-

creasing and decreasing signals. This is due to the fact that

a log amp is a nonlinear gain element and has different gains

FIGURE 6. Current Inverter/Current Source.

LOG101

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SBOS242B

V+

+5V

OPA2335

TLV271 or

I₁

+3.3V

1/2 OPA2335

V_OUT

D₁

Sample

λ₁´

1.5kΩ

LOG101

λ₁

1.5kΩ

+5V

I₂

λ₁

Light

Source

BSH203

D₂

1/2 OPA2335

Back Bias

+3.3V

10nA to 1mA

C_C

LOG101

10nA to 1mA

Pin 1 or Pin 8

Photodiode

V–

FIGURE 9. Absorbance Measurement.

FIGURE 7. Precision Current Inverter/Current Source.

OPERATION ON SINGLE SUPPLY

Many applications do not have the dual supplies required to

operate the LOG101. Figure 10 shows the LOG101 config-

ured for operation with a single +5V supply.

VOLTAGE INPUTS

The LOG101 gives the best performance with current inputs.

Voltage inputs may be handled directly with series resistors,

but the dynamic input range is limited to approximately three

decades of input voltage by voltage noise and offsets. The

transfer function of Equation (13) applies to this configuration.

Single Supply +5V

V_OUT

APPLICATION CIRCUITS

LOG RATIO

I₁

LOG101

One of the more common uses of log ratio amplifiers is

to measure absorbance. A typical application is shown in

Figure 9.

I₂

C_C

Absorbance of the sample is A = logλ₁´/ λ₁

(3)

1µF

If D₁and D₂are matched A (1V) logI₁/I₂

(4)

TPS⁽¹⁾

–5V

1µF

NOTE: (1) TPS60402DBV negative charge pump.

DATA COMPRESSION

In many applications the compressive effects of the logarith-

mic transfer function are useful. For example, a LOG101

preceding a 12-bit Analog-to-Digital (A/D) converter can

produce the dynamic range equivalent to a 20-bit converter.

FIGURE 10. Single +5V Power-Supply Operation.

1.5kΩ

100kΩ

+5V

10nA to 1mA

Back Bias

+3.3V

1/2

OPA2335

+5V

1.5kΩ

1/2

OPA2335

Photodiode

100kΩ

10nA to 1mA

LOG101

Pin 1 or Pin 8

FIGURE 8. Precision Current Inverter/Current Source.

LOG101

SBOS242B

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INSIDE THE LOG101

also

Using the base-emitter voltage relationship of matched

bipolar transistors, the LOG101 establishes a logarith-

mic function of input current ratios. Beginning with the

base-emitter voltage defined as:

R₁+ R₂

V_OUT= V_L

(9)

R₁

R₁+ R₂

I₁

I₂

V_OUT

n V_Tlog

I_C

I_S

(10)

R₁

V_BE= V_Tln

where : V_T=

(1)

k = Boltzman’s constant = 1.381 • 10^–23

T = Absolute temperature in degrees Kelvin

q = Electron charge = 1.602 • 10^–19Coulombs

I_C= Collector current

I₁

I₂

V_OUT= (1V) • log

(11)

I_S= Reverse saturation current

I₂

Q₁

Q₂

–

I₁

From the circuit in Figure 11, we see that:

V_OUT

A₂

V_BEV_BE

I₁

V_L= V_BE– V_BE

(2)

(3)

A₁

I₁

R₂

V_L

R₁

V_OUT= (1V) • LOG

Substituting (1) into (2) yields:

I₂

I₁

V_L= V_T₁ln

– V_T2ln

I_S1

I_S2

If the transistors are matched and isothermal and

V_TI= V_T2, then (3) becomes:

FIGURE 11. Simplified Model of a Log Amplifier.

I₁

V_L= V_T₁ln –ln

I_S

I₂

(4)

(5)

I_S

It should be noted that the temperature dependance

associated with V_T= kT/q is internally compensated on

the LOG101 by making R₁a temperature sensitive resis-

tor with the required positive temperature coefficient.

I₁

V_L= V_Tln and since

I₂

ln x = 2.3log₁₀x

(6)

(7)

I₁

V_L= n V_Tlog

I₂

where n = 2.3

(8)

DEFINITION OF TERMS

TRANSFER FUNCTION

3.5

3.0

2.5

2.0

1.5

1.0

0.5

The ideal transfer function is:

(5)

V_OUT= 1V • log (I₁/I₂)

Figure 12 shows the graphical representation of the transfer

over valid operating range for the LOG101.

0.0

–0.5

–1.0

–1.5

–2.0

–2.5

–3.0

–3.5

I₁

ACCURACY

V_OUT= (1V) • LOG (I₁/I₂)

Accuracy considerations for a log ratio amplifier are some-

what more complicated than for other amplifiers. This is

because the transfer function is nonlinear and has two

inputs, each of which can vary over a wide dynamic range.

The accuracy for any combination of inputs is determined

from the total error specification.

FIGURE 12. Transfer Function with Varying I₂and I₁.

LOG101

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SBOS242B

to I₂is shown in Figure 13. The OPA703 is configured as a

level shifter with inverting gain and is used to scale the

photodiode current directly into the A/D converter input

voltage range.

TOTAL ERROR

The total error is the deviation (expressed in mV) of the

actual output from the ideal output of V_OUT= 1V • log (I₁/I₂).

Thus,

The wide dynamic range of the LOG101 is also useful for

measuring avalanche photodiode current (APD) (see Figure 14).

(6)

V_OUT(ACTUAL)= V_OUT(IDEAL)± Total Error.

It represents the sum of all the individual components of error

normally associated with the log amp when operated in the

current input mode. The worst-case error for any given ratio

of I₁/I₂is the largest of the two errors when I₁and I₂are

considered separately. Temperature can affect total error.

LOG CONFORMITY

For the LOG101, log conformity is calculated the same as

linearity and is plotted I₁/I₂on a semi-log scale. In many

applications, log conformity is the most important specifica-

tion. This is because bias current errors are negligible

(5pA compared to input currents of 100pA and above) and

the scale factor and offset errors may be trimmed to zero or

removed by system calibration. This leaves log conformity as

the major source of error.

ERRORS RTO AND RTI

As with any transfer function, errors generated by the func-

tion itself may be Referred-to-Output (RTO) or Referred-to-

Input (RTI). In this respect, log amps have a unique property:

Log conformity is defined as the peak deviation from the best

fit straight line of the V_OUTversus log (I₁/I₂) curve. This is

expressed as a percent of ideal full-scale output. Thus, the

Given some error voltage at the log amp’s output, that error

corresponds to a constant percent of the input regardless of

the actual input level.

nonlinearity error expressed in volts over m decades is:

(7)

V_OUT(NONLIN)= 1V/dec • 2NmV

USING A LARGER REFERENCE VOLTAGE

REDUCES OFFSET ERRORS

where N is the log conformity error, in percent.

Using a larger reference voltage to create the reference

current minimizes errors due to the LOG101’s input offset

voltage. Maintaining an increasing output voltage as a func-

tion of increasing photodiode current is also important in

many optical sensing applications. All zeros from the

A/D converter output represent zero or low-scale photodiode

current. Inputting the reference current into I₁, and designing

I_REFsuch that it is as large or larger than the expected

maximum photodiode current is accomplished using this

requirement. The LOG101 configured with the reference

current connecting I₁and the photodiode current connecting

INDIVIDUAL ERROR COMPONENTS

The ideal transfer function with current input is:

(8)

I₁

V_OUT= 1V • log

(

)

I₂

The actual transfer function with the major components of

error is:

(9)

I₁– I_B1

V_OUT= 1V 1± ∆K log

± 2Nm ± V_{OS O}

(

)

(

)

I₂– I_B2

V_REF

R₁

R₂

R₃

I_REF

V_OUT= V_REF

–

• (1V)LOG

( )

R₂

R₃

I_PHOTO

C_C

V_OUT

V_MINto V_MAX

I_REF

R₁

I₁

Q₁

Q₂

A/D

Converter

OPA703

A₂

V_REF

A₁

R₂

R₃

I_PHOTO

I₂

LOG101

_MINto I_MAX

FIGURE 13. Technique for Using Full-Scale Reference Current Such that V_OUTIncreases with Increasing Photodiode Current.

LOG101

SBOS242B

www.ti.com

I_SHUNT

+15V to +60V

500Ω

Irx = 1µA to 1mA

Receiver

5kΩ

10Gbits/sec

+5V

APD

I to V

Converter

INA168

SOT23-5

I_OUT= 0.1 • I_SHUNT

I_OUT

C_C

1.2kΩ

1kΩ

+5V

Q₁

Q₂

OPA703

V_OUT= 2.5V to 0V

A₂

A₁

100µA

25kΩ

LOG101

REF3025

2.5V

SO-8

–5V

FIGURE 14. High Side Shunt for Avalanche Photodiode (APD) Measures 3-Decades of APD Current.

The individual component of error is:

Since the ideal output is 1.000V, the error as a percent of

reading is

∆K = gain accuracy (0.15%, typ), as specified in the

specification table.

0.005055

% error =

• 100% = 0.5%

(12)

I_B1= bias current of A₁(5pA, typ)

I_B2= bias current of A₂(5pA, typ)

For the case of voltage inputs, the actual transfer function is

N = log conformity error (0.01%, 0.06%, typ)

0.01% for n = 5, 0.06% for n = 7

E_OS

¹–I_B1

R₁

V₂

R₁

E_OS

V_OUT= 1V 1± ∆K log

± 2Nn ± V_OSO

(

)

(

)

(13)

V_OSO= output offset voltage (3mV, typ)

n = number of decades over which N is specified:

Example: what is the error when

–I_B2

R₂

E_OS2

R₂

^OS1and

Where

are considered to be zero for large

(10)

(11)

I₁= 1µA and I₂= 100nA

10⁻⁶− 5 •10⁻¹²

R₁

values of resistance from external input current sources.

V_OUT= 1± 0.0015 log

± 2 0.00015 ± 3.0mV

(

)

(

)

(

)

10⁻⁷− 5 •10⁻¹²

= 1.005055V

LOG101

www.ti.com

SBOS242B

PACKAGE OPTION ADDENDUM

www.ti.com

9-Dec-2004

PACKAGING INFORMATION

Orderable Device

Status ⁽¹⁾

Package Package

Pins Package Eco Plan ⁽²⁾Lead/Ball Finish MSL Peak Temp ⁽³⁾

Qty

Type

SOIC

Drawing

LOG101AID

ACTIVE

100

None

CU SNPB

Level-3-235C-168 HR

LOG101AIDR

2500

⁽¹⁾The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in

a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2)

Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional

product content details.

None: Not yet available Lead (Pb-Free).

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements

for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered

at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,

including bromine (Br) or antimony (Sb) above 0.1% of total product weight.

(3)

MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder

temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is

provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the

accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take

reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on

incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited

information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI

to Customer on an annual basis.

Addendum-Page 1

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,

enhancements, improvements, and other changes to its products and services at any time and to discontinue

any product or service without notice. Customers should obtain the latest relevant information before placing

orders and should verify that such information is current and complete. All products are sold subject to TI’s terms

and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its hardware products to the specifications applicable at the time of sale in

accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI

deems necessary to support this warranty. Except where mandated by government requirements, testing of all

parameters of each product is not necessarily performed.

TI assumes no liability for applications assistance or customer product design. Customers are responsible for

their products and applications using TI components. To minimize the risks associated with customer products

and applications, customers should provide adequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,

in which TI products or services are used. Information published by TI regarding third-party products or services

does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.

Use of such information may require a license from a third party under the patents or other intellectual property

of the third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of information in TI data books or data sheets is permissible only if reproduction is without

alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction

of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for

such altered documentation.

Resale of TI products or services with statements different from or beyond the parameters stated by TI for that

product or service voids all express and any implied warranties for the associated TI product or service and

is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.

Following are URLs where you can obtain information on other Texas Instruments products and application

solutions:

Products

Applications

Audio

Amplifiers

amplifier.ti.com

www.ti.com/audio

Data Converters

dataconverter.ti.com

Automotive

www.ti.com/automotive

DSP

dsp.ti.com

Broadband

Digital Control

Military

www.ti.com/broadband

www.ti.com/digitalcontrol

www.ti.com/military

Interface

Logic

interface.ti.com

logic.ti.com

Power Mgmt

Microcontrollers

power.ti.com

Optical Networking

Security

www.ti.com/opticalnetwork

www.ti.com/security

www.ti.com/telephony

www.ti.com/video

microcontroller.ti.com

Telephony

Video & Imaging

Wireless

www.ti.com/wireless

Mailing Address:

Texas Instruments

Post Office Box 655303 Dallas, Texas 75265

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LOG101AID产品参数

型号:	LOG101AID
Brand Name：	Texas Instruments
是否无铅：	不含铅
是否Rohs认证：	符合
生命周期：	Active
零件包装代码：	SOIC
包装说明：	SOP, SOP8,.25
针数：	8
Reach Compliance Code：	compliant
ECCN代码：	EAR99
HTS代码：	8542.33.00.01
Factory Lead Time：	1 week
风险等级：	0.94
模拟集成电路 - 其他类型：	LOG OR ANTILOG AMPLIFIER
标称带宽：	0.01 MHz
JESD-30 代码：	R-PDSO-G8
JESD-609代码：	e4
长度：	4.9 mm
湿度敏感等级：	3
负电源电压最大值（Vsup）：	-18 V
负电源电压最小值（Vsup）：	-4.5 V
标称负供电电压 (Vsup)：	-5 V
最大负输入电压：	-3.8 V
功能数量：	1
端子数量：	8
最高工作温度：	85 °C
最低工作温度：	-40 °C
封装主体材料：	PLASTIC/EPOXY
封装代码：	SOP
封装等效代码：	SOP8,.25
封装形状：	RECTANGULAR
封装形式：	SMALL OUTLINE
峰值回流温度（摄氏度）：	260
最大正输入电压：	3.5 V
电源：	+-5 V
认证状态：	Not Qualified
座面最大高度：	1.58 mm
子类别：	Analog Computational Functions
最大供电电流 (Isup)：	1.5 mA
最大供电电压 (Vsup)：	18 V
最小供电电压 (Vsup)：	4.5 V
标称供电电压 (Vsup)：	5 V
表面贴装：	YES
技术：	BIPOLAR
温度等级：	INDUSTRIAL
端子面层：	Nickel/Palladium/Gold (Ni/Pd/Au)
端子形式：	GULL WING
端子节距：	1.27 mm
端子位置：	DUAL
处于峰值回流温度下的最长时间：	NOT SPECIFIED
宽度：	3.91 mm
Base Number Matches：	1

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