LMH6550_14 Datasheet, PDF (16/25 Pages) National Semiconductor (TI) – LMH6550 Differential, High Speed Op Amp

LMH6550
SNOSAK0H – DECEMBER 2004 – REVISED MARCH 2013
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100: TWISTED PAIR
375
200: 2:1 (TURNS)
375
+
a 4 VPP
V_CM
-
375
375
V_CM
200:
1 V_PP
R_L = 100:
A_V = 1
ENABLE
Figure 34. Transformer Out Low Impedance Load
50: COAX
375
100: 2:1 (TURNS)
375
+
a 4 VPP
V_CM
-
375
375
C₁
100:
1 V_PP
ENABLE
GAIN = 1
C₁ IS NOT REQUIRED IF V_CM = GROUND
Figure 35. Driving 50Ω Test Equipment
CAPACITIVE DRIVE
As noted in DRIVING ANALOG TO DIGITAL CONVERTERS, capacitive loads should be isolated from the
amplifier output with small valued resistors. This is particularly the case when the load has a resistive component
that is 500Ω or higher. A typical ADC has capacitive components of around 10 pF and the resistive component
could be 1000Ω or higher. If driving a transmission line, such as 50Ω coaxial or 100Ω twisted pair, using
matching resistors will be sufficient to isolate any subsequent capacitance. For other applications see Figure 8
and Figure 9 in Typical Performance Characteristics.
POWER DISSIPATION
The LMH6550 is optimized for maximum speed and performance in the small form factor of the standard SOIC
package, and is essentially a dual channel amplifier. To ensure maximum output drive and highest performance,
thermal shutdown is not provided. Therefore, it is of utmost importance to make sure that the T_JMAX of 150°C is
never exceeded due to the overall power dissipation.
Follow these steps to determine the Maximum power dissipation for the LMH6550:
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