Datasheet

LMH6629
www.ti.com SNOSB18G –APRIL 2010–REVISED MARCH 2013
The non-inverting circuit is used here as an example. To cancel the bias current errors of the non-inverting
configuration, the parallel combination of the gain setting (R
g
) and feedback (R
f
) resistors should equal the
equivalent source resistance (R
seq
) as defined in Figure 55. Combining this constraint with the non-inverting gain
equation also seen in Figure 55 allows both R
f
and R
g
to be determined explicitly from the following equations:
R
f
= A
V
R
seq
and R
g
= R
f
/(A
V
-1) (2)
Figure 55. Non-Inverting Amplifier Configuration
When driven from a 0Ω source, such as the output of an op amp, the non-inverting input of the LMH6629 should
be isolated with at least a 25Ω series resistor.
As seen in Figure 56, bias current cancellation is accomplished for the inverting configuration by placing a
resistor (R
b
) on the non-inverting input equal in value to the resistance seen by the inverting input (R
f
|| (R
g
+R
s
)).
R
b
should to be no less than 25Ω for optimum LMH6629 performance. A shunt capacitor (not shown) can
minimize the additional noise of R
b
.
Figure 56. Inverting Amplifier Configuration
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