THS6012_16 Datasheet, PDF (19/37 Pages) Texas Instruments – 500-mA DUAL DIFFERENTIAL LINE DRIVER

THS6012
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SLOS226F – SEPTEMBER 1998 – REVISED JUNE 2012
resistance increases, the output resistance of the amplifier becomes less dominant at high frequencies. To
compensate for this, the feedback resistor should change. For 100-Ω loads, it is recommended that the feedback
resistor be changed to 820 Ω for a gain of 1 and 560 Ω for a gain of 2 or -1. Although, for most applications, a
feedback resistor value of 1 kΩ is recommended, which is a good compromise between bandwidth and phase
margin that yields a very stable amplifier.
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. Therefore, once a frequency response is found suitable to a particular application, adjust the value of
the gain resistor to increase or decrease the overall amplifier gain.
Finally, 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.
OFFSET VOLTAGE
The output offset voltage, (V_OO) is the sum of the input offset voltage (V_IO) and both input bias currents (I_IB) times
the corresponding gains. The following schematic and formula can be used to calculate the output offset voltage:
Figure 40. Output Offset Voltage Model
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