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Application Section
FIGURE 7. External Lag Compensation
SINGLE SUPPLY OPERATION
The LMH6624 can be operated with single power supply as
shown in Figure 8. Both the input and output are capacitively
coupled to set the DC operating point.
FIGURE 8. Single Supply Operation
LOW NOISE TRANSIMPEDANCE AMPLIFIER
Figure 9 implements a low-noise transimpedance amplifier
commonly used with photo-diodes. The transimpedance
gain is set by R
. Equation 4 provides the total input current
f
noise density (i
) equation for the basic transimpedance
ni
configuration and is plotted against feedback resistance (R
showing all contributing noise sources in Figure 10. This plot
indicates the expected total equivalent input current noise
density (i
) for a given feedback resistance (R
ni
equivalent output voltage noise density (e
(Continued)
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)
f
). The total
f
) is i
*
R
.
no
ni
f
15
FIGURE 9. Transimpedance Amplifier Configuration
FIGURE 10. Current Noise Density vs. Feedback
Resistance
LOW NOISE INTEGRATOR
The LMH6624 implements a deBoo integrator shown in
Figure 11. Positive feedback maintains integration linearity.
The LMH6624's low input offset voltage and matched inputs
allow bias current cancellation and provide for very precise
integration. Constraint on the circuit element maintains sta-
bility.
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