Features

Easy to use, complete function

Output zoom amplifier

2.5V voltage benchmark on the film

High -precision: 0.2%FSO [5.2%FSO [ 123]

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

Low static current: 1.75ma

Power supply range Wide: ± 4.5V to ± 18V

] Packaging: SO-14 (narrow) and SO-16

Application

Dialog 123] Optical diode signal compression amplifier

The front -end analog signal compression

Model converter

Inhalation of lighting measurement

Optical level measurement

Explanation

log1112 and log21112 are the number or pair ratio of the input current of the multifunctional integrated circuit compared to the reference current. VLOG112 and LOG2112 are adjusted to 0.5V per ten years, ensuring high -precision signals within the wide dynamic input range. LOG112 and LOG2112 have a 2.5V voltage benchmark, which can be used to generate the benchmark for accurate current using external resistors. Low-DC offset voltage and temperature drift are allowed to measure low-level signals within a prescribed temperature range from -5 ° C to+75 ° C

Note The compensation gain changes with the temperature. The VCM pin is connected to the GND in LOG2112.

Electrical features

Black bodies are limited to the specified temperature range, TA --5 ° C to+75 ° C.

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

Note: (1) The consistency error of the number is the peak deviation of the optimal fit line of VO and the number (I1/I2) curve Output peak percentage representation. K. The proportional factor is equivalent to an input current 0.5V output every ten years.

(2) The label factor of the core function of the core function is adjusted to 0.5V output input current every ten years.

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

(4) The total error includes offset voltage, bias current, gain, and number consistency.

(5) Bandwidth (3DB) and transient response are function currents for compensation capacitors and input levels.

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 is VO and LOG (I1/i2) curve the best bias of the best fit line. Between percentage represents the output. K. The proportional factor is equivalent to an input current 0.5V output every ten years.

(2) The standard factor of the core function of the core function is adjusted to an input change of 0.5V output every decade

current.

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

(4) The total error includes offset voltage, bias current, gain, and number consistency.

(5) Bandwidth (3DB) and transient response are function currents for compensation capacitors and input levels.

Typical features

TA +25 ° C, vs ± 5V, RL 10K

Application information

LOG112 is a real number amplifier. It uses bipolar crystal tube base to emit the pole The voltage relationship calculates the number or number ratio of the mobile ratio. Figure 1 and 2 show the operations required for the operations for LOG112 and LOG2112. In order to reduce the influencing line of the power supply inductance, it is recommended to connect 10 μF 钽 capacitor capacitors in parallel with 1000PF ceramics, as shown in Figure 1 and Figure 2. Capacitors connected to LOG112 and LOG2

Input current range

In order to maintain the specified accuracy, the input current range LOG112 and LOG2112 should be limited to 100Pa to 3.5 mm install. The input current exceeding this range may be damaged LOG1112 performance. The input current is greater than 3.5mA and the non -linear increase. The maximum input rated current is 10mA to prevent too much power from damaging the loss of the input transistor. On the ± 5V power supply, the total input current (i1+i2) is limited to 4.5 mAh. Due to the log 112 and log2112, to adapt to a larger total input current, the power supply should increase.

Set reference current

When LOG112 and LOG2112 are used to calculate LOGA Rithms, i1 or i2 can remain unchanged, thus becoming a reference current compared with another. Vlogout tableShow as: vlogout (0.5V) number (I1/Iref) (1) IREF can from the external current source (as shown in Figure 3), or it can be derived from the voltage with one or more resistors with one or more resistors. power supply. 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 device can be used to reduce

resistance, As shown in Figure 4. When using this method, you must consider the error input offset voltage that the amplifier may cause. The maximum value of the input bias voltage of the amplifier A1 is 1.5mV. It is recommended to use the VREF A value of 100mV.

FIG. 5 shows a series of low -electric flat -current source resistors using a series. Low offset operational amplifier reduces the input offset voltage of log1112 and log21112

frequency response

The frequency response curve in the typical characteristic curve shows the constant DC I1 and i2 and a small signal AC current with an input end. The 3DB frequency response of LOG112 and LOG2112 is to compensate the capacitor value in the input current and frequency. See the typical characteristic curve, 3DB frequency response details. The transient response of LOG112 and LOG2112 is to increase and reduce signals. This is because the number amplifier is a different gain under different input signal levels of non -linear gain elements. Smaller input current requires a larger gain to maintain a full dynamic range, and will slow down the frequency response of LOG1112 and log21112.

Frequency compensation

The frequency compensation of log1112 is connected to the capacitor between the pin 5 and 14. Compensation of frequency LOG2112 adopts capacitors between connection pins 2 and 5, or capacitors between 15 and 12. 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 capacitor that can be used by minimum value can be used by the maximum value of i2 and the minimum value of i1. The larger CC value makes LOG112 and LOG2112 more stable, but the frequency response is reduced. In the application, the highest total bandwidth can be obtained by detecting the signal level of VOUT, and then the capacitors that connect the appropriate compensation value

negative input current

LOG112 and LOG2112 are only under positive input in the input Positioning current (traditional current flows into the input current). In the case of negative input current, the circuit in Figure 6, 7 and 8 can be used

Voltage input

] LOG112 and LOG2112 input at the current.The voltage input can be directly connected with series resistance, but the dynamic input range is limited to about 30 years input voltage noise and offset. The transmission function of equation 13 is used here. When the input current of LOG1112 is increased with a higher input current, the output accuracy degenerates. For the 4.5mA input current to ± 5V power and 10mA input current ± 12V power, the total output error can be between 15%and 25%. A co -mode voltage with at least+1V to 2.5V is applied on the VCM, which can obtain the recorded crystal unsaturated and reduce the output error to about 10%. In order to avoid the positive bias of the optoelectronics diode, the cathode is returned to the VCM pin, as shown in Figure 9. To the reverse bias photoresal diode, the cathode is better than the anatomy. A more common use of the number of application circuits than the amplifier is to measure the absorbance. For typical applications, see Figure 10. The inhalation of the sample is A A number of λ1 ′/λ1 (3) If D1 and D2 match, A∞ (0.5V) logi1/i2

Data compression

In many applications, the compression effect of the digital transmission function is useful. For example, the top 12 A/D converter of LOG112 can generate a dynamic range equivalent to the range of 20 -bit converters.

Single power operation

Many applications do not need dual -power operation LOG112 and LOG2112. Figure 11 shows the configuration of log112 and log21112 to use a single+5V power supply. The large dynamic range of LOG1112 and LOG21112 of the avalanche photoresal diode current is used to measure the avalanche optical diode current (APD), as shown in Figure 12.

The term definition

The transmission function

[[ 123] The ideal transmission function is: vlogout (0.5V) number (i1/i2)

FIG. 14 shows the effective working range of the transmitted graphics that exceeds LOG112 and LOG2112.

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 deviation of the actual value (represented by MV) output of the ideal output of Vlogout (0.5V) log (I1/i2). Therefore, vlogout (actual) vlogout (ideal) ± total error (6)

It represents the sum of all error components and the current amplifier in the current input mode. Any givenThe worst situation of ratio is the most incorrect situation of I1 and i2 as a separate consideration. Temperature will affect the total error.

Error RTO and RTI

Like any transmission function, an error generated by this function can be called output (RTO) or input (RTI). In this regard, there is a unique feature of the number amplifier: given some error voltage at the output end of the number amplifier, which corresponds to the constant percentage of the input, regardless of the actual input level.

Log compliance

For LOG112 and LOG2112, calculate the same LOG consistency and linear, and draw i1/i2 on the semi -pairing scale. In many applications, log consistency is the most important specification. This is true, because the bias current error can be ignored (5Pa compared to the 100Pa input current can be trimmed to zero proportional factor and offset error or remove through system calibration. The main source of errors. For the peak deviation of the number compliance with the peak deviation of the optimal value, the straight line of the number (I1/I2) curve of the number (I1/I2). The non -linear error of the M -year is: vlogout (nonlin) 0.5V/DEC u0026#8226; 2 millival (7) where n is the log consistency error, which is expressed in a percentage

A single error component

] The ideal transmission function of the current input is:

The main component of the actual transmission function is:

The single component part of the error is:

] u0026#8710; k gain error (0.10%, typical value), as shown in the specification table.

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

ib2 IB2 A2's bias current (5Pa, typical value)

n Consistency error of numbers (0.01%, 0.13%, typical value)

m 5 o'clock is 0.01%, m m, m, m, m, m, m, m, m 7.5 is 0.13%

VOSO Output offset voltage (3MV, typical value)

M decate for decision n What is the error:

i1 1 μA and I2 100NA