from matplotlib.pyplot import *
from numpy import *

RC, peak = 1., 1.
Vdd, Vss, T, duty = peak, -peak, 2.*log(3.)*RC, .5
Tmax, lim = 3.*T, .01
totalT = linspace(0,Tmax,150)
Vo, Vc, out, vc, n = [], [], Vss, 0., 0.
for x in totalT:
 vc = out * (1. - exp(-x+n*T*.5))
 Vo = append(Vo,out)
 Vc = append(Vc,vc)
 if (vc >= Vdd*0.5) or (vc <= Vss*0.5):
  out = -out
  n = n + 1.
Vr = Vo * 0.5

fig = figure(figsize=(8,4))
ax = fig.add_subplot(111)
ax.grid(True)
ax.plot(totalT,Vo, label=r"$V_{\mathrm{out&#x7D;&#x7D;$")
ax.plot(totalT,Vr, label=r"$V_R$")
ax.plot(totalT,Vc, label=r"$V_C$")
ax.legend(loc='upper right',bbox_to_anchor=(.955,1.),\
 frameon=False,handletextpad=.05)
ax.set_ylim(-1.1,1.1)
ax.minorticks_on()
ax.set_xlim(0,Tmax)
ax.set_xlabel("t",fontsize=15)
ax.set_ylabel("Voltage")

fig.savefig("Opamprelaxationoscillator.png",bbox_inches="tight",\
 pad_inches=.15)