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 ]

低静态电流：1mA

供电范围广：±4.5V至±18V

应用

对数，对数比计算：通信、分析、 Medical, Industry, Test, General Instrument

Optical diode signal compression amplifier

The front -end analog signal compression

Model converter

Instructions

LOG104 is a pair or number reference current of the input current of the general integrated circuit compared to the input current. LOG104 performed a test signal 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 trimmed to 0.5V input current every ten years, allowing 70 years of input current and dynamic range. Low -current offset voltage and temperature drift allows the measurement temperature range of low level signals under precise width environment. The temperature range of LOG104 is -5 ° C to+75 ° C, and the operating temperature range is -40 ° C to+75 ° C+85 degrees Celsius.

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 an input current change of 0.5V output 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 is a function of compensating capacitors and input current levels.

Typical features

TA +25 ° C, vs ± 5V, RL 10K

Application information

LOG104 is a real number amplifier. It uses bipolar crystal tube base to emit the pole Calculation ratio ratio or number ratio of voltage relationship. Figure 1 shows the basic connection log 104 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 LOG104 as much as possible.

Input current range

In order to maintain the specified accuracy, the input current range LOG104 should be limited to between 100Pa and 3.5mA. The input current beyond this range may affect the performance of LOG104. The input current greater than 3.5mA can cause non -linearity. Absolute maximum input current contains ± 10mA to prevent excessive power consumption from damaging the well -measured transistor. On the ± 5V power supply, the total input current (i1+i2) is limited to 4.5 mAh. Because the compliance problem inside the log104 adapts to a large total input current, the power supply should increase. A current of less than 100Pa will cause error to increase the input bias current (usually 5Pa) of the input bias (usually 5Pa) of the computing amplifier A1 and A2. 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 log104 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 (0.5V) number (I1/I2) (1) IREF can be from the external current source (as shown in Figure 3), or from the voltage band from the voltage band There is a 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

4 shown). 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 operations reduce the input offset voltage of LOG104.

Frequency response

The frequency response curve in the typical characteristic curve shows the small signal AC current of the frequency response curve of the constant DC i1 and i2. The 3DB frequency response of LOG104 is the size and frequency compensation capacitor of the input current level. See the typical feature curve, 3DB frequency response details. The transient response of LOG104 is different for increased and reduced signals. This is because the number amplifier is a non -linear gain component, with different gains of different gains and different input levels. The smaller input current requires a larger gain to maintain a complete dynamic range and slow down the frequency response of LOG104.

Frequency compensation

The frequency compensation of log104 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 log104 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. The negative input current LOG104 works only at the time of the 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

LOG104 under current input. Best performance. 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

A 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 Drive λ1 ′/λ1 (3) If D1 and D2 match, A∞ (0.5V) logi1/i2 (4) The data is compressed to many applications, and the compression effect of the number transmission function is useful. Essence For example, the first 12 -bit A/D converter of LOG104 can generate a dynamic range equivalent to the range of 20 -bit converters.

The single power supply operation

Many applications do not need the dual -power operation log104. Figure 10 shows the log104 configuration running under a single+5V power supply.

Using the basal voltage matching relationship of the basis of the basis

LOG104 establishes a number function of the input 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 crystal is matched and the temperature VTI VT2, then (3) becomes:

[ 123]

The term definition

The transmission function

The ideal transmission function is: voltage 0.5v 12 exceeds the effective work scope of LOG104.

accuracy

For some amplifiers, accuracy comparison is more complicated than the number amplifier. 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 of the ideal output of Vout 0.5V log (I1/I2) Essence 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.

Measurement of the avalanche optoelectronics diode current

The broad dynamic range of log104 helps measure the avalanche optoelectronic diode current (APD), as shown in Figure 13.

Log compliance

For LOG104, 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 true, because the bias current error can be ignored (5Pa compared to 100Pa or above input current), proportional factor and offset error can be trimmed to zero or systematic calibration deleted deleted deleteEssence This makes the main source of log consistency errors. For the straight line of the number of peak deviations of the number compliance with the optimal value deviation of the optimal value deviation. 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) 0.5V/dec 2nm v, where n is the log consistency error, which is represented by percentage.

A single error component

The ideal transmission function of the current input is:

The main component of the actual transmission function is the error of the error Yes:

The single component 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 values)

n 5 o'clock is 0.01%, n 7.5 is 0.06%

voso output offset voltage (3mv, typical value value, typical value )

M Specifying the number of N decades of n:

Example: What is the error

The resistance value of the external input current source.