ltc2195 Linear Technology Corporation, ltc2195 Datasheet - Page 18

• Manufacturer Part Number: ltc2195
• Description: Ltc2195/ltc2194/ltc2193 - 16-bit, 125/105/80msps Low Power Dual Adcs
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LTC2195
LTC2194/LTC2193
DC level. At higher input frequencies a transmission line
balun transformer (Figures 4 to 6) has better balance,
resulting in lower A/D distortion.
Amplifier Circuits
Figure 7 shows the analog input being driven by a high
speed differential amplifier. The output of the amplifier is AC
coupled to the A/D so the amplifier’s output common mode
voltage can be optimally set to minimize distortion.
At very high frequencies an RF gain block will often have
lower distortion than a differential amplifier. If the gain
block is single ended, then a transformer circuit (Figures 4
to 6) should convert the signal to differential before driv-
ing the A/D.
18
ANALOG
Figure 4. Recommended Front-End Circuit for Input Frequencies
from 5MHz to 150MHz
INPUT
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz
ANALOG
INPUT
0.1µF
0.1µF
0.1µF
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1L
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
T1
1:1
T1
T2
25
25
25
25
0.1µF
50
25
25
0.1µF
50
12
12
0.1µF
12pF
V
A
A
CM
IN +
IN –
0.1µF
8.2pF
V
A
A
CM
IN +
IN –
LTC2195
219543 F03
LTC2195
219543 F04
ANALOG
Figure 5. Recommended Front-End Circuit for Input Frequencies
from 150MHz to 250MHz
Figure 6. Recommended Front-End Circuit for Input Frequencies
Above 250MHz
ANALOG
INPUT
ANALOG
INPUT
INPUT
Figure 7. Front-End Circuit Using a High Speed
Differential Amplifier
0.1µF
0.1µF
DIFFERENTIAL
0.1µF
0.1µF
HIGH SPEED
+
–
AMPLIFIER
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1L
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
T1: MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
T1
T1
0.1µF
0.1µF
T2
25
25
200
25
25
50
4.7nH
4.7nH
0.1µF
200
25
25
0.1µF
50
0.1µF
0.1µF
12pF
12pF
V
A
A
CM
IN +
IN –
A
A
V
IN +
IN –
0.1µF
1.8pF
CM
V
A
A
CM
IN +
IN –
LTC2195
LTC2195
LTC2195
219543 F06
219543 F07
219543p
219543 F05