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參數(shù)資料
| 型號(hào)： | ICL8049BCJE |
| 廠商： | HARRIS SEMICONDUCTOR |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | Antilog Amplifier |
| 中文描述： | LOG OR ANTILOG AMPLIFIER, CDIP16 |
| 文件頁(yè)數(shù)： | 3/3頁(yè) |
| 文件大?。?/td> | 521K |
| 代理商： | ICL8049BCJE |
3
ICL8049
ICL8049 Detailed Description
The ICL8049 relies on the same logarithmic properties of
the transistor as the ICL8048. The input voltage forces a
specific
V
BE
between Q
1
and Q
2
(Figure 1). This V
BE
difference is converted into a difference of collector currents
by the transistor pair. The equation governing the behavior
of the transistor pair is derived from (2) on the previous page
and is as follows:
(1)
When numerical values for q/kT are put into this equation, it
is found that a
V
BE
of 59mV (at +25
o
C) is required to
change the collector current ratio by a factor of ten. But for
ease of application, it is desirable that a 1V change at the
input generate a tenfold change at the output. The required
input attenuation is achieved by the network comprising R
1
and R
2
. In order that scale factors other than one decade
per volt may be selected, R
2
is external to the chip. It should
have a value of 1k
, adjustable
±
20%, for one decade per
volt. R
1
is a thin film resistor deposited on the monolithic
chip; its temperature characteristics are chosen to
compensate the temperature dependence of Equation 1, as
explained on the previous page.
The overall transfer function is as follows:
(2)
Substituting V
OUT
= I
OUT
x R
OUT
gives:
(3)
--------
exp
q
-----------------
=
IOUT
IREF
---------
exp
+
R1
R2
(
)
---------------------
---------
kT
×
=
VOUT
ROUTIREFexp
+
R1
R2
)
------–
------------
×
=
For voltage references Equation 3 becomes
(4)
ICL8049 Offset and Scale Factor
Adjustment
As with the log amplifier, the antilog amplifier requires three
adjustments. The first step is to null out the offset voltage of
A
2
. This is accomplished by reverse biasing the base-emitter
of Q
2
. A
2
then operates as a unity gain buffer with a
grounded input. The second step forces V
IN
= 0; the output is
adjusted for V
OUT
= 10V. This step essentially “anchors” one
point on the transfer function. The third step applies a
specific input and adjusts the output to the correct voltage.
This sets the scale factor. Referring to Figure 1 the exact
procedure for 1 decade/volt is as follows:
1. Connect the input (pin #16) to +15V. This reverse biases
the base-emitter of Q
2
. Adjust R
7
for V
OUT
= 0V. Discon-
nect the input from +15V.
2. Connect the input to Ground. Adjust R
4
for V
OUT
= 10V.
Disconnect the input from Ground.
3. Connect the input to a precise 2V supply and adjust R
2
for
V
OUT
= 100mV.
The procedure outlined above optimizes the performance
over a 3 decade range at the output (i.e., V
OUT
from 10mV)
to 10V). For a more limited range of output voltages, for
example 1V to 10V, it would be better to use a precise 1V
supply and adjust for V
OUT
= 1V. For other scale factors and/
or starting points, different values for R
2
and R
REF
will be
needed, but the same basic procedure applies.
VOUT
VREF
ROUT
RREF
-----------
×
exp
R
+
2
R1
R2
(
)
-----–
qVIN
---------
kT
×
=
FIGURE 1. ICL8049 OFFSET AND SCALE FACTOR ADJUSTMENT
A
1
+
-
A
2
+
-
R
7
2k
V+
1k
200pF
I
REF
13
12
15
3
7
16
1
10
14
Q
1
Q
2
R
5
15k
R
2
R
1
15.9k
2
V
IN
V+
V-
R
REF
15k
C
1
V
REF
(+15V)
I
OUT
V
OUT
R
OUT
10k
R
6
100k
R
3
15k
680
(LOW
T.C.)
R
4
2k
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ICL8049C | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| ICL8049C/D DIE | 制造商:Harris Corporation 功能描述: |
| ICL8049CCJE | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:Antilog Amplifier |
| ICL8049CCJE WAF | 制造商:Harris Corporation 功能描述: |
| ICL8049CCPE | 制造商:ICS 功能描述: 制造商:INTRSL 功能描述: 制造商:Rochester Electronics LLC 功能描述: |
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