Voltage follower

$\parbox{3.0in}{\raisebox{-2.5in}{\par \hbox{\hskip 0in \vbox to 2.5in{\includegraphics[height=2.5in]{FIGS/fig2.2.ps}\vfill}}}}$ $\parbox{3in}{% Connect one of the 353 op-amps as a voltage follower.... ... \hline & & \hline & & \hline & & \hline \end{tabular}\end{center}}$

$\parbox{2.0in}{\raisebox{-1.5in}{\par \hbox{\hskip 0in \vbox to 1.5in{\includegraphics[height=1.5in]{FIGS/fig2.3.ps}\vfill}}}}$ $\parbox{3.5in}{% A $1 $k$\Omega$ resistor will be used in series w... ... voltage at point $A$ with and without the $10 $k$\Omega$ load connected. }$

$\parbox{2.0in}{\raisebox{-1.5in}{\par \hbox{\hskip 0in \vbox to 1.5in{\includegraphics[height=1.5in]{FIGS/fig2.4.ps}\vfill}}}}$ $\parbox{3.5in}{% Now connect an op-amp voltage follower (353) to buf... ...output voltage with and without the $10 $k$\Omega$ load resistor connected. }$

A transducer has an output resistance of $80$k$\Omega$. Describe how a follower could be used to decrease the loading error if the transducer output voltage is to be measured with a $1$M$\Omega$ input resistance oscilloscope and indicate the percent error avoided.

$\parbox{2.0in}{\raisebox{-1.0in}{\par \hbox{\hskip 0in \vbox to 1.0in{\includegraphics[height=1.0in]{FIGS/fig2.5.ps}\vfill}}}}$ $\parbox{3.5in}{% Fix the input voltage at $+10 $V. Connect a $1 $k... ...oltage with the DMM. Remove $R_{\rm load}$ and measure the no-load voltage. }$

Repeat using the $100 \Omega$ and $47 \Omega$ load resistors. Calculate the output current for each case.

$R_{\rm load}$	$V_{\rm out}$, with load	$V_{\rm out}$, without load	$I_{\rm out}$, with load

The small output voltage change observed with the $1$k$\Omega$ load indicates the very low output resistance of the voltage follower. At lower load resistance, it is possible to exceed the maximum output current capability of the op-amp. A significant loading of the output voltage occurs in such a case.

On the basis of the change in output voltage with a $1$k$\Omega$ load, estimate the output resistance of the voltage follower, or if no change was observed, place an upper limit on the output resistance, i.e. calculate the value the output resistance would have if the smallest observable change had been measured. It may help to draw an equivalent circuit for the op-amp (see Simpson, Fig.9.21 or Faissler, Chapters 29 and 31).

Calculate the maximum output current the op-amp can supply, based on your observations with the $100 \Omega$ and $47 \Omega$ loads.