91Ó°ÊÓ

In your own words, describe a situation in which a small differential signal is of interest and a large common-mode signal is also present.

A certain amplifier has a differential gain of 1000 . If the two input terminals are tied together and a \(5-\mathrm{mV}-\mathrm{rms}\) input signal is applied, the output signal is \(30 \mathrm{mV} \mathrm{rms}\). Find the CMRR for this amplifier.

In a certain instrumentation amplifier, the input signal consists of a \(20-\mathrm{mV}-\mathrm{rms}\) differential signal and a 5-V-rms 60-Hz interfering common-mode signal. It is desired that the common-mode contribution to the output signal be at least \(60 \mathrm{~dB}\) lower than the contribution from the differential signal. What is the minimum CMRR allowed for the amplifier in decibels?

A differential amplifier has a differential gain of 500 and negligible common- mode gain. The input terminals are tied to ground through \(1-\mathrm{k} \Omega\) resistors having tolerances of \(\pm 5\) percent. What are the extreme values of the output voltage caused by a bias current of \(100 \mathrm{nA}\) ? What is the output voltage if the resistors are exactly equal?

A differential amplifier has a bias current of \(100 \mathrm{nA}\), a maximum offset current of 20 \(\mathrm{nA}\), a maximum offset voltage of \(2 \mathrm{mV}\), an input resistance of \(1 \mathrm{M} \Omega\), and a differential gain of 1000 . The input terminals are tied to ground through (exactly equal) 100 \(\mathrm{k} \Omega\) resistors. Find the extreme values of the output voltage if the common-mode gain is assumed to be zero.