ICL8048BCJE View Datasheet(PDF) - Intersil
Part Name
Description
Manufacturer
ICL8048BCJE Datasheet PDF : 8 Pages
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ICL8048
Typical Performance Curves (Continued)
100K
IREF = 1mA
10K
1K
100
10
10-11
10-9
10-7
10-5
INPUT CURRENT (A)
10-3
FIGURE 3. SMALL SIGNAL BANDWIDTH vs INPUT
CURRENT
200
175
150
125
100
8048BC (0oC TO 70oC)
75
50
8048BC (25oC)
25
0
10-9
10-8
10-7
10-6
10-5
10-4
10-3
INPUT CURRENT (A)
FIGURE 4. MAXIMUM ERROR VOLTAGE AT THE OUTPUT vs
INPUT CURRENT
200
RIN = 10kΩ
175
150
125
100
8048BC (0oC TO 70oC)
75
50
25
8048BC (25oC)
0
10mV
100mV
1V
10V
INPUT VOLTAGE (V)
FIGURE 5. MAXIMUM ERROR VOLTAGE AT THE OUTPUT vs
INPUT VOLTAGE
ICL8048 Detailed Description
The ICL8048 relies for its operation on the well known
exponential relationship between the collector current and
the base emitter voltage of a transistor:
IC
=
IS
ex
p
q----V-k---T-B----E--
–
1
(EQ. 1)
For base emitter voltages greater than 100mV, Equation 1
becomes
IC = IS expq----V-k----BT----E--
(EQ. 2)
From Equation 2, it can be shown that for two identical
transistors operating at different collector currents, the VBE
difference (∆VBE) is given by:
∆VBE
=
-2.303
×
k----T--
q
l
o g10
I--C-----1--
IC2
(EQ. 3)
1000
434
100
10
VOLTAGE GAIN
RIN = 10kΩ
=
∆VIN
∆VOUT
=
log10 e
VIN
=
4343
VIN
V/V
1
0.1
0.01
1mV
10mV
100mV
1V
10V
INPUT VOLTAGE (V)
FIGURE 6. SMALL SIGNAL VOLTAGE GAIN vs INPUT
VOLTAGE FOR RS = 10kΩ
Referring to Figure 7 it is clear that the potential at the
collector of Q2 is equal to the ∆VBE between Q1 and Q2.
The output voltage is ∆VBE multiplied by the gain of A2:
VOUT
=
-2.303
R-----1---R--+--2---R----2--
k--q--T--
lo
g10
----I--I--N------
IREF
(EQ. 4)
The expression 2.303 × k----T-- has a numerical value of 59mV at
25oC;
thus
in
order
to
q
generate
1V/decade
at
the
output,
the
ratio (R1 + R2)/R2 is chosen to be 16.9. For this scale factor
to hold constant as a function of temperature, the
(R1 + R2)/R2 term must have a 1/T characteristic to
compensate for kT/q.
In the ICL8048 this is achieved by making R1 a thin film
resistor, deposited on the monolithic chip. It has a nominal
value of 15.9kΩ at 25oC, and its temperature coefficient is
3
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