Current-to-voltage converter

$\parbox{2.0in}{\raisebox{-1.5in}{\par \hbox{\hskip 0in \vbox to 1.5in{\includegraphics[height=1.5in]{FIGS/fig3.1.ps}\vfill}}}}$ $\parbox{3.35in}{% Wire up the current-t... ... = -R_{f} I_{\rm in}\end{displaymath}Use a feedback resistor of 10 k$\Omega$. }$

Use a 10 M$\Omega$ precision resistor in series with a variable voltage supply as the current source: $I_{\rm in} = V_{\rm in}\times 10^{-7}$, for several (five or more) input currents in the nanoamperes-to-microamperes range. Measure $V_{\rm out}$ with the DMM.

$I_{\rm in}$	Calculated $V_{\rm out}$	Measured $V_{\rm out}$	% error

Will the input offset voltage affect the measurement of small currents more (a) when the current source is a small voltage and a small resistance, or (b) when it is a large voltage and a large resistance?

$\parbox{2.0in}{\raisebox{-1.0in}{\par \hbox{\hskip 0in \vbox to 1.0in{\includegraphics[height=1.0in]{FIGS/fig3.2.ps}\vfill}}}}$ $\parbox{4.5in}{% Using a signal diode 1N914, wire the following inpu... ... & \hline 2 V & & & \hline 5 V & & & \hline \end{tabular}\end{center}}$