LMH6551Q Datasheet, PDF (13/20 Pages) Texas Instruments – Differential, High Speed Op Amp

With up to 15 V_PP differential output voltage swing and 80 mA
of linear drive current the LMH6551Q makes an excellent ca-
ble driver as shown in Figure 2. The LMH6551Q is also
suitable for driving differential cables from a single ended
source.
30157910
FIGURE 3. Single Ended in Differential Out
30157912
FIGURE 5. Single Supply Bypassing Capacitors
The LMH6551Q requires supply bypassing capacitors as
shown in Figure 4 and Figure 5. The 0.01 µF and 0.1 µF ca-
pacitors should be leadless SMT ceramic capacitors and
should be no more than 3 mm from the supply pins. The SMT
capacitors should be connected directly to a ground plane.
Thin traces or small vias will reduce the effectiveness of by-
pass capacitors. Also shown in both figures is a capacitor from
the V_CM pin to ground. The V_CM pin is a high impedance input
to a buffer which sets the output common mode voltage. Any
noise on this input is transferred directly to the output. Output
common mode noise will result in loss of dynamic range, de-
graded CMRR, degraded Balance and higher distortion. The
V_CM pin should be bypassed even if the pin in not used. There
is an internal resistive divider on chip to set the output com-
mon mode voltage to the mid point of the supply pins. The
impedance looking into this pin is approximately 25kΩ. If a
different output common mode voltage is desired drive this
pin with a clean, accurate voltage reference.
30157901
FIGURE 4. Split Supply Bypassing Capacitors
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