LTC6421-20
Dual Matched
1.3GHz Differential
Amplifiers/ADC Drivers
FEATURES
DESCRIPTION
TheLTC®6421-20isadualhighspeeddifferentialamplifier
targeted at processing signals from DC to 140MHz. The
part has been specifically designed to drive 12-, 14- and
16-bitADCswithlownoiseandlowdistortion,butcanalso
be used as a general-purpose broadband gain block.
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Matched Gain 0.1dB
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Matched Phase 0.2° at 100MHz
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Channel Separation 80dB at 100MHz
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1.3GHz –3dB Bandwidth; Fixed Gain of 10V/V (20dB)
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IMD = –76dBc at 100MHz, 2V
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P-P
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Equivalent OIP = 42dBm at 100MHz
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The LTC6421-20 is easy to use, with minimal support
circuitry required. The output common mode voltage
is set using an external pin, independent of the inputs,
whicheliminatestheneedfortransformersorAC-coupling
capacitors in many applications. The gain is internally
fixed at 20dB (10V/V).
1nV/√Hz Internal Op Amp Noise
6.2dB Noise Figure
Differential Inputs and Outputs
Rail-to-Rail Output Swing
40mA Supply Current (120mW) per Amplifier
1V to 1.6V Output Common Mode Voltage,
Adjustable
DC- or AC-Coupled Operation
20-Lead 3mm × 4mm × 0.75mm QFN Package
The LTC6421-20 saves space and power compared to
alternativesolutionsusingIFgainblocksandtransformers.
The LTC6421-20 is packaged in a compact 20-lead
3mm × 4mm QFN package and operates over the –40°C
to 85°C temperature range.
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APPLICATIONS
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Differential ADC Driver
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Differential Driver/Receiver
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Single Ended to Differential Conversion
IF Sampling (Diversity) Receivers
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TYPICAL APPLICATION
Matched Dual Amplifiers with Output Common Mode Biasing
3V
1000pF 0.1μF
V
V
OCMA
OCMA
Distribution of Gain Match
+
V
A
ENABLEA
Z
IN
= 200Ω
0.1μF
LTC6421-20
40
35
30
25
20
15
10
5
1000Ω
100Ω
100Ω
12.5Ω
12.5Ω
–INA
+OUTA
–OUTA
V
V
OCMA
OCMA
V
INA
0.1μF
+INA
–
–
1000Ω
1000Ω
V
V
0.1dB GAIN MATCHING
0.1° PHASE MATCHING
AT 100MHz
0.1μF
0.1μF
100Ω
100Ω
12.5Ω
12.5Ω
+INB
–INB
–OUTB
+OUTB
V
V
OCMB
OCMB
V
INB
0
–0.25 –0.15 –0.05
0.05
0.15
0.25
CHANNEL-TO-CHANNEL GAIN MATCH (dB)
1000Ω
Z
= 200Ω
IN
642120 TA01b
+
V
B
V
OCMB
ENABLEB
642120 TA01a
1000pF
0.1μF
V
OCMB
3V
642120fa
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