THS6002 Datasheet, PDF (37/40 Pages) Texas Instruments – DUAL DIFFERENTIAL LINE DRIVERS AND RECEIVERS

THS6002
DUAL DIFFERENTIAL LINE DRIVERS AND RECEIVERS
SLOS202D– JANUARY 1998– REVISED JULY 1999
APPLICATION INFORMATION
general configurations (continued)
RG
RF
VI
R1
–
+
C1
ǒ Ǔǒ Ǔ + ) ₎ ^VO
VI
1
RF
RG
1
1
sR1C1
VO
+ f–3dB
1
2pR1C1
Figure 61. Single-Pole Low-Pass Filter
If a multiple pole filter is required, the use of a Sallen-Key filter can work very well with CFB amplifiers. This is
because the filtering elements are not in the negative feedback loop and stability is not compromised. Because
of their high slew-rates and high bandwidths, CFB amplifiers can create very accurate signals and help minimize
distortion. An example is shown in Figure 62.
C1
VI
R1
+
R2
_
C2
RF
RG
R1 = R2 = R
C1 = C2 = C
Q = Peaking Factor
(Butterworth Q = 0.707)
+ f–3dB
1
2pRC
( ) ^{RG =}
RF
1
2–
Q
Figure 62. 2-Pole Low-Pass Sallen-Key Filter
There are two simple ways to create an integrator with a CFB amplifier. The first one shown in Figure 63 adds
a resistor in series with the capacitor. This is acceptable because at high frequencies, the resistor is dominant
and the feedback impedance never drops below the resistor value. The second one shown in Figure 64 uses
positive feedback to create the integration. Caution is advised because oscillations can occur because of the
positive feedback.
RG
VI
RF
C1
–
+
VO
THS6002
ǒ Ǔ_{ȧȡ ȧȣ} + ^{) VO}
RF
S
1
RFC1
Ȣ Ȥ ^VI
RG
S
Figure 63. Inverting CFB Integrator
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