LMH6601_14 Datasheet, PDF (20/37 Pages) National Semiconductor (TI) – LMH6601/LMH6601Q 250 MHz, 2.4V CMOS Operational Amplifier with Shutdown

LMH6601, LMH6601-Q1
SNOSAK9E – JUNE 2006 – REVISED MARCH 2013
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OVERLOAD RECOVERY AND SWING CLOSE TO RAILS
The LMH6601 can recover from an output overload in less than 20 ns. See Figure 50 below for the input and
output scope photos:
V_S = ±2.5V
INPUT (4 V_PP) OUTPUT (1V/DIV)
TIME (10 ns/DIV)
Figure 50. LMH6601 Output Overload Recovery Waveform
In Figure 50, the input step function is set so that the output is driven to one rail and then the other and then the
output recovery is measured from the time the input crosses 0V to when the output reaches this point.
Also, when the LMH6601 input voltage range is exceeded near the V⁺ rail, the output does not experience output
phase reversal, as some op amps do. This is particularly advantageous in applications where output phase
reversal has to be avoided at all costs, such as in servo loop control among others. This adds to the LMH6601’s
set of features which make this device easy to use.
In addition, the LMH6601’s output swing close to either rail is well-behaved as can be seen in the scope photo of
Figure 51.
0V
0V
V_S = ±2.5V
1 ms/DIV
Figure 51. LMH6601’s “Clean” Swing to Either Rail
With some op amps, when the output approaches either one or both rails and saturation starts to set in, there is
significant increase in the transistor parasitic capacitances which leads to loss of Phase Margin. That is why with
these devices, there are sometimes hints of instability with output close to the rails. With the LMH6601, as can
be seen in Figure 51, the output waveform remains free of instability throughout its range of voltages.
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