MAX4206ETE+T Maxim Integrated Products, MAX4206ETE+T Datasheet - Page 10

• Manufacturer Part Number: MAX4206ETE+T
• Description: IC AMP TRANS LOG 16-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX4206ETE+T

• Amplifier Type: Logarithmic
• Number Of Circuits: 1
• Slew Rate: 12 V/µs
• Gain Bandwidth Product: 5MHz
• Voltage - Input Offset: 1000µV
• Current - Supply: 5mA
• Current - Output / Channel: 58mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 11 V, ±2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Number Of Channels: 1
• Input Offset Voltage: 5 mV
• Operating Supply Voltage: 3 V, 5 V, 9 V
• Supply Current: 5 mA
• Operating Temperature Range: + 85 C
• Mounting Style: SMD/SMT
• Power Dissipation: 1349 mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• -3db Bandwidth: -
• Current - Input Bias: -
• Lead Free Status / Rohs Status: Details

Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
Figure 1. Functional Diagram
Figure 2 shows a simplified model of a logarithmic
amplifier. Two transistors convert the currents applied
at LOGIIN and REFIIN to logarithmic voltages accord-
ing to the following equation:
where:
The logarithmic amplifier compares V
ence voltage V
known reference current, I
10
V
k = 1.381 x 10
T = absolute temperature (K)
q = 1.602 x 10
I
I
C
S
BE
______________________________________________________________________________________
= reverse saturation current
= collector current
= base-emitter voltage of a bipolar transistor
LOGIIN
CMVIN
REFIIN
GND
V
EE
BE2
-23
V
–19
, which is a logarithmic voltage for a
BE
J/K
C
=
Detailed Description



kT
q
REF
V
V
V
CC
CC
EE



. The temperature depen-
ln



I
I
C
S



BE1
MAX4206
to the refer-
Theory
CORRECTION
CURRENT
V
CC
COMPENSATION
TEMPERATURE
SUMMING
AMPLIFIER
REFVOUT
1.238V
dencies of a logarithmic amplifier relate to the thermal
voltage, (kT/q), and I
the I
following manner:
AND
S
temperature dependence of the amplifier in the
CMVOUT
0.5V
V
=
=
=
=
= ×
OUT












K
kT
kT
kT
kT
q
q
q
q
log












=
ln
(
ln( )
V











ln
ln
10
BE
I
10
LOG









V
1
I
CURRENT MIRROR
I
I
S
I
LOG
LOG
CC
REF
I
I
−
LOG
S
I
)
REF
S
. Matched transistors eliminate
V





 −

BE
log
V
V

 −




CC
EE



 



2



10
kT
ln
q









I
I
I
LOG
REF
REF
ln
I
S



I
REF



I



S








REFIOUT
REFISET
LOGV2
SCALE
OSADJ
LOGV1



(
see Figure
3
)