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參數(shù)資料
| 型號： | ICL8048BCJE |
| 廠商： | INTERSIL CORP |
| 元件分類： | 運動控制電子 |
| 英文描述： | Log Amplifier |
| 中文描述： | LOG OR ANTILOG AMPLIFIER, CDIP16 |
| 封裝： | FRIT SEALED, CERDIP-16 |
| 文件頁數(shù)： | 5/7頁 |
| 文件大?。?/td> | 85K |
| 代理商： | ICL8048BCJE |
5
Figure 9 shows the ICL8048 in an automatic offset nulling
configuration using the ICL7650S. The extremely low offset
voltage of the ICL7650S forces its non-inverting input (and thus
pin 2 of the ICL8048) to the same potential as its inverting input
by nulling the first stage of the log amp. Since V
OFFSET
is now
within a few
μ
V of ground potential, R
IN
can perform its voltage
to current conversion much more accurately, and without an
offset trimmer pot. Step 1 of the offset and scale factor
adjustment is eliminated, simplifying calibration.
NOTE: The ICL7650S op amp has a maximum supply voltage of
18V. The ICL8048 will operate at this voltage, but I
REF
must be
limited to 200
μ
A or less for proper calibration and operation. Best
performance will be achieved when the ICL7650S has a
±
3V to
±
8V
supply and the ICL8048 is at its recommended
±
15V supply. See
A053 for a method of powering the ICL7650S from a
±
15V source.
Frequency Compensation
Although the op amps in the ICL8048 are compensated for
unity gain, some additional frequency compensation is
required. This is because the log transistors in the feedback
loop add to the loop gain. In the ICL8048, 150pF should be
connected between Pins 2 and 7 (Figure 7).
Error Analysis
Performing a meaningful error analysis of a circuit containing a
log and antilog amplifiers is more complex than dealing with a
similar circuit involving only op amps. In this data sheet every
effort has been made to simplify the analysis task, without in
any way compromising the validity of the resultant numbers.
The key difference in making error calculations in log/antilog
amps, compared with op amps, is that the gain of the former
is a function of the input signal level. Thus, it is necessary,
when referring errors from output to input, or vice versa, to
check the input voltage level, then determine the gain of the
circuit by referring to the graphs given in the Typical
Performance Curves section.
The various error terms in the log amplifier, the ICL8048, are
Referred To the Output (RTO) of the device. The errors are
expressed in this way because in the majority of systems a
number of log amps interface with an antilog amp, as shown
in Figure 10.
It is very straightforward to estimate the system error at node
(A) by taking the square root of the sum-of-the-squares of
the errors of each contributing block.
If required, this error can be referred to the system output
through the voltage gain of the antilog circuit, using the
voltage gain versus input voltage plot.
The numerical values of x, y, and z in the above equation are
obtained from the maximum error voltage plots. For
example, with the ICL8048BC, the maximum error at the
output is 30mV at 25
o
C. This means that the measured
output will be within 30mV of the theoretical transfer
function, provided the unit has been adjusted per the
procedures described previously. Figure 11 illustrates this
point.
ICL7650
+
-
+
-
A
1
+
-
A
2
I
REF
I
IN
R
IN
V
IN
V
OUT
ICL8048
Q
1
Q
2
V
OFFSET
0.1
μ
F
0.1
μ
F
0.1
μ
F
33k
33k
0V
1K
4
5
2
1
16
10
7
15
V
(+15V)
R
REF
R
3
A
1
OUTPUT
R
5
2k
R
1
15.9k
R
2
680
(LOW T.C.)
1k
C
1
150pF
GAIN
V+
FIGURE 9. ICL8048 OFFSET NULLED BY ICL7650
12
13
A
INPUT
INPUT
ERROR DUE TO B (RTO)
= ymV
ERROR DUE TO C (RTI)
= zmV
ERROR DUE TO A (RTO)
= xmV
ANTI LOG
AMP
C
LOG AMP
A
LOG AMP
B
OUTPUT
FIGURE 10.
Total Error
x2
y2
z2
+
+
at (A)
=
ICL8048
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|---|---|
| ICL8048 | Log Amplifier |
| ICL8069CCZQ | Low-Voltage Reference |
| ICL8069DCZQ | Low-Voltage Reference |
| ICL8069DESA | Low-Voltage Reference |
| ICL8069CCSA | Low-Voltage Reference |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ICL8048C | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| ICL8048C/D DIE | 制造商:Harris Corporation 功能描述: |
| ICL8048CJE | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| ICL8049 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:N-CHANNEL JFET |
| ICL8049BCJE | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:Antilog Amplifier |
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