THS4561 Datasheet, PDF (15/35 Pages) Texas Instruments – Low-Power, High Supply Range, 70-MHz, Fully Differential Amplifier

www.ti.com
THS4561
SBOS874 – AUGUST 2017
Example Characterization Circuits (continued)
• Translating from a 1-kΩ differential load to a 50-Ω environment introduces considerable insertion loss in the
measurements (–31.8 dB in Figure 1). The measurement path insertion loss normalizes when reporting the
frequency response curves to show the gain response to the FDA output pins.
• In the pass band for the output balun, the 50-Ω load of the network analyzer reflects in parallel with the 52.3-
Ω shunt termination. These elements combine to show a differential 1-kΩ load at the output pins of the
THS4561. The source impedance presented to the balun is a differential 50-Ω source. Figure 2 and Figure 3
show the TINA-TI™ model (available as a TINA-TI™ simulation file) and resulting response flatness for this
relatively low-frequency balun providing 0.1-dB flatness through 100 MHz.
ADTL1-4-75 Model 198.94µ
R1
25
L1
+
VG1
±
R2
25
L2
+
R3
VM1
50
L1 Inductance: 198.94 µH
L2 Inductance: 198.94 µH
Mutual Inductance: 198.92972 µH
Figure 2. Output Measurement Balun Simulation Circuit in TINA-TI™
-6
10
-6.01
8
-6.02
6
-6.03
4
-6.04
2
-6.05
0
-6.06
-2
-6.07
-4
-6.08
-6.09
-6.1
1k
Gain (dB)
Phase (deg)
10k
100k
1M
Frequency (Hz)
10M
-6
-8
-10
100M
D061
Figure 3. Output Measurement Balun Flatness Test
Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: THS4561
Submit Documentation Feedback
15