LMH6654 Datasheet, PDF (17/31 Pages) National Semiconductor (TI) – Single/Dual Low Power, 250 MHz, Low Noise Amplifiers

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LMH6654, LMH6655
SNOS956E – JUNE 2001 – REVISED AUGUST 2014
Typical Application (continued)
7.2.2.2 Bias Current Cancellation
In order 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 42.
Combining this constraint with the non-inverting gain equation, allows both R_f and R_g to be determined explicitly
from the following equations:
R_f = A_VR_seq and R_g = R_f/(A_V−1)
(2)
For inverting configuration, bias current cancellation is accomplished 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). The additional noise contribution of
R_b can be minimized through the use of a shunt capacitor.
Figure 42. Non-Inverting Amplifier Configuration
Figure 43. Inverting Amplifier Configuration
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