THS6184_16 Datasheet, PDF (20/39 Pages) Texas Instruments – DUAL-PORT, LOW-POWER DIFFERENTIAL xDSL LINE DRIVER AMPLIFIERS

THS6184
SLLS635D – AUGUST 2005 – REVISED JANUARY 2009 ................................................................................................................................................. www.ti.com
DIE
Side View (a)
DIE
End View (b)
Thermal
Pad
Bottom View (c)
A. The thermal pad is electrically isolated from all terminals in the package.
Figure 52. Views of Thermally Enhanced PWP Package
(Representative Only – Not to Scale)
RECOMMENDED FEEDBACK AND GAIN RESISTOR VALUES
As with all current feedback amplifiers, the bandwidth of the THS6184 is an inversely proportional function of the
value of the feedback resistor. The recommended resistors with a ±12-V power supply for the optimum frequency
response with a 100-Ω load system is 2 kΩ for a gain of 5. These should be used as a starting point and once
optimum values are found, 1% tolerance resistors should be used to maintain frequency response
characteristics.
Consistent with current feedback amplifiers, increasing the gain is best accomplished by changing the gain
resistor, not the feedback resistor. This is because the bandwidth of the amplifier is dominated by the feedback
resistor value and internal dominant-pole capacitor. The ability to control the amplifier gain independently of the
bandwidth constitutes a major advantage of current feedback amplifiers over conventional voltage feedback
amplifiers.
It is important to realize the effects of the feedback resistance on distortion. Increasing the resistance decreases
the loop gain and increases the distortion. It is also important to know that decreasing load impedance increases
total harmonic distortion (THD). Typically, the third order harmonic distortion increases more than the second
order harmonic distortion.
Finally, in a differential configuration as shown in Figure 1, it is important to note that there is a differential gain
and a common-mode gain which are different from each other. Differentially, the gain is at 1 + 2R_F/R_G. While
common-mode gain = 1 due to R_G being connected directly between each amplifier and not to ground.
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