An inverting amplifier is built with from the source to the inverting input and from…

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing · Feedback, operational amplifiers and analogue signal processing

Electronics for Measurement, Ch The operational amplifier and negative feedback

Problem

An inverting amplifier is built with

R_1 = 5\,\mathrm{k}\Omega

from the source to the inverting input and

R_f = 100\,\mathrm{k}\Omega

from the output back to the inverting input. The operational amplifier has a gain-bandwidth product

f_T = 3\,\mathrm{MHz}

and a slew rate

\mathrm{SR} = 0.4\,\mathrm{V\,\mu s^{-1}}

. A sine wave of frequency

15\,\mathrm{kHz}

is applied so that the output peak amplitude is

8\,\mathrm{V}

. ((a)) Use the two rules of the ideal amplifier to find the closed-loop gain

A_{\rm CL}

. ((b)) Someone argues: "the closed-loop

-3\,\mathrm{dB}

bandwidth at this gain is

f_T/|A_{\rm CL}|

, which comes out far above

15\,\mathrm{kHz}

, so the sine wave will be reproduced without distortion." Decide whether this conclusion is correct, and if not, say what limits the output and estimate the largest frequency at which an

8\,\mathrm{V}

peak sine can still be reproduced without distortion.

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