Page 78 - Op Amps Design, Applications, and Troubleshooting

Noninverting Amplifier 61

The voltage gain can be computed by the basic gain equation, Equation (2.1), as
shown:

Recall from an earlier discussion that the voltage gain of the circuit is largely
determined by the ratio of R F to R/. More specifically, the low-frequency or ideal
voltage gain of the circuit can also be calculated with the following equation:

In our case, the calculations are

This latter method is the most common, but the former provides additional
insight into circuit operation and the application of basic electronics principles.
The voltage can be expressed in decibels if desired, as we did with inverting
amplifiers. In our present example, the equivalent voltage gain expressed in deci-
bels is:

Note that the voltage gain computed in this section is the ideal closed-loop voltage
gain of the circuit. The actual circuit gain will roll off as the input frequency is
increased, just as it did with inverting amplifiers. This effect is discussed below as
part of the discussion on bandwidth.