THS4031_16 Datasheet, PDF (24/47 Pages) Texas Instruments – THS403x 100-MHz Low-Noise High-Speed Amplifiers

THS4031, THS4032
SLOS224H – JULY 1999 – REVISED JUNE 2016
www.ti.com
R_G
R_F
V_I
R1
−
+
V_O
C1
f–3dB
+
1
2pR1C1
ǒ Ǔǒ Ǔ ^VO
VI
+
1
)
RF
RG
1
1 ) sR1C1
Figure 57. Single-Pole Low-Pass Filter
If even more attenuation is needed, a multiple-pole filter is required. The Sallen-Key filter can be used for this
task. For best results, the amplifier should have a bandwidth that is 8 to 10 times the filter frequency bandwidth.
Otherwise, phase shift of the amplifier can occur.
C1
V_I
R1
+
R2
_
C2
R_F
R_G
R1 = R2 = R
C1 = C2 = C
Q = Peaking Factor
(Butterworth Q = 0.707)
f–3dB
+
1
2pRC
( ) ^{RG =}
R_F
1
2– _Q
Figure 58. Two-Pole Low-Pass Sallen-Key Filter
9.4 Device Functional Modes
9.4.1 Offset Nulling
The THS403x has very low input offset voltage for a high speed amplifier. However, if additional correction is
required, the designer can make use of an offset nulling function provided on the THS4031. By placing a
potentiometer between terminals 1 and 8 of the device and tying the wiper to the negative supply, the input offset
can be adjusted. This is shown in Figure 59.
V_CC+
3
+
7
THS4031
2_{_}
4
8
1 _{10 k Ω}
0.1 mF
0.1 mF
V_CC −
Figure 59. Offset Nulling Schematic
24
Submit Documentation Feedback
Copyright © 1999–2016, Texas Instruments Incorporated
Product Folder Links: THS4031 THS4032