\documentclass{standalone}
\usepackage[american]{circuitikz}
\usepackage{graphicx}
\usepackage{mathrsfs} 
\usepackage{latexsym,amssymb,amsmath}
\newcommand{\equal}{=}
\begin{document}
		\begin{circuitikz}
		%\draw (0,4) to [open,v^>=$v_1(t)$,o-o]  (0,0) -- Open Short
		\draw (0,6) to [open,l_=$e_i$,o-o]  (0,1) % input
			(0,6) to  [C, l_= $C$,-*] (2,6)	%C
			(1,6) node[] (Z2) {}	% used for drawing rectangle
			(2,6) to  [R, l_=$R_1$,-*] (2,1)	%R1
			node[] (Z2end) {}	% used for drawing rectangle
			(2,1) -- (2,0.5) node[ground]{}	%ground
			(5, 5.5) node[op amp] (opamp) {}
			(2,	6) to [open, -*] (3.5,6) node[above]{$A$}
			(2,6) -- (opamp.-) 
		     (3.5,5) node[left]{$B$} to [short,*-] 	(opamp.+)
		     (opamp.out)  to [short,-*]  (6.5,5.5)
		     node[] (Z1) {}	% used for drawing rectangle
		     to [R, l^=$R_2$,-*] (6.5,3) %R2
		     to [R, l^=$R_3$, -*] (6.5,1)
		      node[] (Z1end) {} % used for drawing rectangle
		     (6.5,3) -- (3.5,3)	% connect B to middle of resistors
		     (3.5,3) -- (3.5,5)	% vertical connection to B
			(6.5,5.5) -- (7.5,5.5)
			(7.5,5.5) to [open,l^=$e_o$,o-o]  (7.5,1) % output
			(0,1) -- (7.5,1) % wire
			;
			\draw[thick,dotted]     ($(Z1.north west)+(-0.5,0.15)$) rectangle ($(Z1end.south east)+(0.5,-0.15)$);
			\draw (Z1.north) +(0,0.5) node {$Z_1$};
			\draw[thick,dotted]     ($(Z2.north west)+(-0.5,0.25)$) rectangle ($(Z2end.south east)+(0.5,-0.15)$);
			\draw (Z2.north) +(0,0.5) node {$Z_2$};
	\end{circuitikz}
\end{document}