Datasheet

LTC2261-12
LTC2260-12/LTC2259-12
19
226112fc
For more information www.linear.com/LTC2261-12
applicaTions inForMaTion
Figure 5. Recommended Front-End Circuit for Input
Frequencies from 170MHz to 270MHz
Figure 6. Recommended Front-End Circuit for Input
Frequencies Above 270MHz
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.
Figure 4. Recommended Front-End Circuit for Input
Frequencies from 70MHz to 170MHz
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.
25Ω
25Ω
50Ω
0.1µF
A
IN
+
A
IN
–
1.8pF
0.1µF
V
CM
ANALOG
INPUT
0.1µF
0.1µF
T1
T2
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1LB
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
226112 F05
LTC2261-12
25Ω
25Ω
50Ω
0.1µF
A
IN
+
A
IN
–
4.7pF
0.1µF
V
CM
ANALOG
INPUT
0.1µF
0.1µF
T1
T2
T1: MA/COM MABA-007159-000000
T2: MA/COM MABAES0060
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
226112 F04
LTC2261-12
25Ω
25Ω
50Ω
0.1µF
2.7nH
2.7nH
A
IN
+
A
IN
–
0.1µF
V
CM
ANALOG
INPUT
0.1µF
0.1µF
T1
T1: MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
226112 F06
LTC2261-12