Operational Amplifier Fundamentals Unit 3 – The Noninverting Amplifier
Exercise 3 – Noninverting Amplifier Response
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the gain/bandwidth
characteristics of a noninverting operational amplifier. You will verify your results with an
oscilloscope.
EXERCISE DISCUSSION
- Gain-bandwidth (GBW) product and slew rate (SR) are two op amp specifications that affect
the operation of a noninverting amplifier. Slew rate will be examined in another unit. - For a noninverting amplifier, circuit gain multiplied by circuit band- width cannot exceed the
specified GBW product of the circuit op amp. - As the gain of the amplifier increases, circuit bandwidth decreases.
- As the gain of the amplifier decreases, circuit bandwidth increases.
- If the amplifier bandwidth is limited, its output voltage falls off (is reduced or attenuated),
and the waveform may be distorted. - The LF441 op amp has a specified GBW product of 1 MHz.
- A capacitor placed across the circuit feedback resistor reduces the bandwidth ac gain of the
amplifier and ac gain becomes frequency dependent. - The breakpoint frequency of this circuit occurs at the frequency where XC (in ohms) equals
the value of R2. - The breakpoint is referred to as the -3 dB point of the circuit and defines the circuit
bandwidth frequency. - At the -3 dB point of a circuit, the output voltage is attenuated by the factor 0.707 (0.707 x
VO). - The formula dB = 20 log (VNEW/VINITIAL) expresses the change in output voltage.
- VNEW is the final output voltage at the operating frequency, such as 100 kHz, where the
output voltage has decreased by 0.707. - VINITIAL is the starting output voltage at the reference frequency, such as 1 kHz.