LMH6654 Datasheet, PDF (20/31 Pages) National Semiconductor (TI) – Single/Dual Low Power, 250 MHz, Low Noise Amplifiers

LMH6654, LMH6655
SNOS956E – JUNE 2001 – REVISED AUGUST 2014
8 Power Supply Recommendations
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8.1 Power Dissipation
The package power dissipation should be taken into account when operating at high ambient temperature and/or
high power dissipative conditions. In determining maximum operable temperature of the device, make sure the
total power dissipation of the device is considered; this power dissipated in the device with a load connected to
the output as well as the nominal dissipation of the op amp.
9 Layout
9.1 Layout Guidelines
With all high frequency devices, board layouts with stray capacitance have a strong influence on the AC
performance. The LMH6654/LMH6655 are not exception and the inverting input and output pins are particularly
sensitive to the coupling of parasitic capacitance to AC ground. Parasitic capacitances on the inverting input and
output nodes to ground could cause frequency response peaking and possible circuit oscillation. Therefore, the
power supply, ground traces and ground plan should be placed away from the inverting input and output pins.
Also, it is very important to keep the parasitic capacitance across the feedback to an absolute minimum.
The PCB should have a ground plane covering all unused portion of the component side of the board to provide
a low impedance path. All trace lengths should be minimized to reduce series inductance.
Supply bypassing is required for the amplifiers performance. The bypass capacitors provide a low impedance
return current path at the supply pins. They also provide high frequency filtering on the power supply traces. It is
recommended that a ceramic decoupling capacitor 0.1 µF chip should be placed with one end connected to the
ground plane and the other side as close as possible to the power pins. An additional 10 µF tantalum electrolytic
capacitor should be connected in parallel, to supply current for fast large signal changes at the output.
V⁺
10 µF
+
0.1 µF
0.1 µF
+
10 µF
-
V
Figure 46. Supply Bypass Capacitors
9.1.1 Evaluation Boards
TI provides the following evaluation boards as a guide for high frequency layout and as an aid in device testing
and characterization.
DEVICE
LMH6654MF
LMH6654MA
LMH6655MA
LMH6655MM
PACKAGE
5-Pin SOT-23
8-Pin SOIC
8-Pin SOIC
8-Pin VSSOP (DGK)
EVALULATION BOARD PN
LMH730216
LMH730227
LMH730036
LMH730123
20
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