Features

Easy to use complete core function

High -precision: 0.01%FSO

Wide input dynamic range: 7.5 years, 100Pa to 3.5ma [123 123 ]

Low static current: 1MA

The range of power supply is wide: ± 4.5V to ± 18V

Division, the number ratio calculation:

123] Communication, analysis, medical care, industry, testing and general instruments

Optical diode signal compression amplifier

The front -end simulation signal compression

Model number converter

[ 123] Explanation

LOG101

is a pair or number reference current of the input current of the general integrated circuit compared to the input current. LOG101 test signals within a large dynamic input range. In the pairing ratio application, the signal current will appear from the optoelectronics diode, and the reference current comes from a series with precision external benchmark. The output signal is adjusted to the output voltage to the 1V current every ten years to allow the 70 -year dynamic input current range. Low -current offset voltage and temperature drift allows the measurement temperature range of low level signals under precise width environment. LOG101 specifies the temperature range of -5 ° C to+75 ° C, and operates more than -40 ° C to+85 ° C.

Electrical characteristics

Black body limit is suitable for the specified temperature range, TA --5 ° C to+75 ° C.

TA +25 ° C, vs ± 5V, rout 10k unless there is another explanation.

Electrical characteristics (continued)

Black body limit is suitable for the specified temperature range, TA --5 ° C to+75 ° C.

TA +25 ° C, vs ± 5V, RL 10K

Note: (1) The consistency error of the number refers to the peak bias of VOUT and pair (i1/i2) curve best fitting straight line, and use a full standard. The percentage of Du Peak is expressed.

(2) A higher power supply may be required in the full dynamic range.

(3) The output core -to -number function is adjusted to the 1V output of the input current every ten years.

(4) When considering I1 and I2, the total error of the worst situation of any I1/i2 ratio is the largest of the two errors.

(5) In the ± 5V power, the total I1+I2 should be kept below 4.5mA.

(6) Bandwidth (3DB) and transient response areCompensation capacitors and functions of input current levels.

Typical features

TA +25 ° C, vs ± 5V, RL 10K

Typical features (continued)

TA +25 ° C, vs ± 5V, RL 10K Essence

Application information

LOG101 is a real pairing amplifier. It uses bipolar transistors to emit the polar voltage relationship with the voltage relationship. Division ratio. Figure 1 shows the basic connection log 101 required for the operation. In order to reduce the inductance of the influencing power cord, each power is recommended to use a 10μF 钽 capacitor to bypass parallel with 1000pf ceramic capacitors, as shown in the medium. Connect the capacitor to the position near LOG101 as much as possible.

Input current range

In order to maintain the specified accuracy, the input current range LOG101 should be limited to between 100Pa and 3.5mA. The input current beyond this range may affect the performance of LOG101. The input current greater than 3.5mA can cause non -linearity. The absolute maximum input current set includes 10mA, which prevents excessive power transistors from damaging the well. On the ± 5V power supply, the total input current (i1+i2) is limited to 4.5 mAh. Because the internal compliance problems of LOG101 adapt to a large total input current, the power supply should increase. The current less than 100Pa will cause an error to increase the input bias current of the operation amplifier A1 and A2 (usually 5Pa). The input bias current can be compensated, as shown in Figure 2. The input level of the amplifier is FET input, and the input bias current doubles every 10 ° C, which makes zero adjustment technology only stable at the temperature.

Set the reference current

When log101 is used to calculate the number of pairs, i1 or i2 can be kept constant and become another comparison with another. VOUT is expressed as: vout (1V) Number (I1/I2) (1)

Iref can be from the external current source (as shown in Figure 3), or from the voltage bands from the voltage bands The power of one or more resistors. When a resistor is used, the value may be large, depending on Iref. If IREF uses 10NA and+2.5V: RREF 2.5V/10NA 250m

The pressure 分 can be used to reduce the resistance, as shown in Figure 4. When using this method, you must consider the error input offset voltage that the amplifier may cause. The input voltage of the amplifierThe maximum value is 1.5mV. It is recommended to use the VREF A value of 100mV.

FIG. 5 shows a low -electric flat current source using a series

resistor. Low offset operations reduce the input offset voltage of LOG101.

Frequency response

The frequency response curve seen in the typical characteristic curve shows the signal AC current of the constant DC i1 and i2 input. The 3DB frequency response of LOG101 is the size and frequency compensation capacitor of the input current level. See the typical feature curve 3DB frequency response to obtain detailed information. The transient response of LOG101 is different for increased and reduced signals. This is because the number amplifier is a non -linear gain element, which has different gains at different levels of input signals. The smaller input current requires a larger gain to maintain a complete dynamic range and slow down the frequency response of LOG101.

Frequency compensation

The frequency compensation of log101 is connected to the capacitor between the pin 3 and 8. The large and small electrical container is a function of the input current, such as the typical characteristic curve (the minimum value of the capacitor). For any given application, the minimum useable capacitor value consists of the maximum value of i2 and the minimum value of i1. The larger CC value will make the log101 more stable, but the frequency response will be reduced. In the application, the highest total bandwidth can be obtained by detecting the signal level of VOUT, and then connects the appropriate value of compensation capacitors.

Negative input current

LOG101 is only working at the time at the time of input current (traditional current flows into needle 1 and 8). When a negative input current is required in some cases, the circuit can use Figure 6, 7, and 8.

Voltage input

LOG101 has the best performance under current input. The voltage input can be handled directly with a series resistance, but the dynamic input range is limited to about three decades of input voltage caused by voltage noise and offset. This (13) transmission function is suitable for this structure.

Application circuit

A number ratio

One more common use of the number ratio amplifier is to measure the absorbance. Typical applications are shown in Figure 9. The inhalation of the sample is A A number of λ1 ′/λ1 (3) If D1 and D2 match, then A∞ (1V) logi1/i2

Data compression

In many applications, right, right The compression effect of the number transmission function is useful. For example, LOG101 produces a dynamic range equivalent to 20 -bit converters before the 12 -bit modulus converter.

Single power operation

Many applications do not have the need to dual power

Operation log101. Figure 10 shows the LOG101 configuration of a single+5V power supply

Using the basis of the basal voltage matching relationship

bipolar crystal tube, log101 establishes input input The numbers of the current ratio. The definition of the polar voltage from the base is:

k Bolitzman constant 1.381 10–23

t Absolute temperature, unit: Kaishi degree

q electronic charge 1.602 10–19 Kulun

IC collection electrode current

IS reverse saturation current

from from the obsession The circuit in Figure 11 can be seen:

If the transistor matches and is equivalent to VTI VT2, then (3) becomes:

[ 123] It should be noted that internal compensation related to the temperature dependence and VT KT/Q makes R1 a temperature -sensitive resistor with the required positive temperature coefficient to achieve log101.

The definition of the term

The transmission function

The ideal transmission function is: voltage 1V The effective working scope of log101.

accuracy

The accuracy of numbers is more complicated than other amplifiers. This is because the transmission function is a non -linear input, and each one can change within a large dynamic range. Determine the accuracy of any input combination from the total error specification.

Total error

The total error is the actual output value of the ideal output 1V log (i1/i2). Therefore, VOUT (actual) vout (ideal) ± total error. It represents the sum of all error components and the current amplifier in the current input mode. The worst situation of any given ratio is the worst case of I1 and i2 as a separate consideration. Temperature will affect the total error. Error RTO and RTI Like any transmission function, errors produced by the function itself can be called output (RTO) or input (RTI). In this regard, there is a unique feature of the number amplifier: the error voltage of the given amplifier output terminal is corresponding to the constant percentage of the input, regardless of the actual input level. The use of larger reference voltage reduction errors use larger reference voltage to create a benchmark current to minimize the error voltage caused by the input offset of LOG101. Keep an increased output voltage as an increase in optoelectricityThe function of diode current is in many optical sensing applications. Output from the A/D converter represents zero or low -standard photoelectric diode current. The reference current input i1 and design IREF to make it as much as expected or larger as the maximum photovoltaic diode current. The LOG101 current connection I1 and the optoelectronics diode current connection are used in Figure 13. OPA703 is configured as a level transform with a reversal gain, which is used to zoom in optical diode current directly input A/D converter voltage range. LOG101's wide dynamic range is also suitable for measuring the avalanche optoelectronics diode (APD) (see Figure 14).

Log compliance

For log101, the calculation method and linearity of the number of consistency are drawn, and I1/i2 is drawn on the semi -pairing scale. In many aspects of applications, log consistency is the most important specification. This is because the bias current error can be ignored (5PA compared to 100Pa or above input current) and the proportional factor and offset error can be trimmed to zero or it has been calibrated by the system. This makes the log consistency

The main source of error.

The straight line of the summary vout and log (i1/i2) curve of the peak deviation of the number compliance with the number of numbers is defined as the optimal value. This is the percentage of the ideal full -scale output. Therefore, the nonlinear error of the M -year -in -law represented by Volter is: the output voltage (nonlin) 1v/dec 2nmv where n is the log consistency error, which is represented by percentage. The ideal transmission function of a single error component current input is:

The single component part of the error is:

] u0026#8710; k gain accuracy (0.15%, typical value), such as specification table.

The bias current of IB1 A1 (5Pa, typical value)

The bias current of IB2 A2 (5Pa, typical value)

n Consistency of the pair of pairs Sexual errors (0.01%, 0.06%, typical value)

n 5 is 0.01%, n 7 is 0.06%

voso output offset voltage (3mv, typical value) [) 123]

N Specify the decades of N:

Example: What is the error

Because the ideal output is 1.000V, the error is the error is to be the error is Reading is

The resistance value of the external input current source.