Analog Circuits

Discharging capacitor

Shows how to connect to a switch with anchors.

../_images/analog_1_0.svg
d = schemdraw.Drawing()
d += (V1 := elm.SourceV().label('5V'))
d += elm.Line().right().length(d.unit*.75)
d += (S1 := elm.SwitchSpdt2(action='close').up().anchor('b').label('$t=0$', loc='rgt'))
d += elm.Line().right().at(S1.c).length(d.unit*.75)
d += elm.Resistor().down().label('100 Ω').label(['+','$v_o$','-'], loc='bot')
d += elm.Line().to(V1.start)
d += elm.Capacitor().down().at(S1.a).toy(V1.start).label('1 μF')
d += elm.Dot()
d.draw()

Capacitor Network

Shows how to use endpoints to specify exact start and end placement.

../_images/analog_2_0.svg
d = schemdraw.Drawing(fontsize=12)
d += (A := elm.Dot().label('a'))
d += (C1 := elm.Capacitor().label('8nF'))
d += (C2 := elm.Capacitor().label('18nF'))
d += (C3 := elm.Capacitor().down().label('8nF', loc='bottom'))
d += (C4 := elm.Capacitor().left().label('32nF'))
d += (C5 := elm.Capacitor().label('40nF', loc='bottom'))
d += (B := elm.Dot().label('b'))
d += (C6 := elm.Capacitor().endpoints(C1.end, C5.start).label('2.8nF'))
d += (C7 := elm.Capacitor().endpoints(C2.end, C5.start)
      .label('5.6nF', loc='center', ofst=(-.3, -.1), halign='right', valign='bottom'))
d.draw()

ECE201-Style Circuit

This example demonstrate use of push() and pop() and using the ‘tox’ and ‘toy’ methods.

../_images/analog_3_0.svg
d = schemdraw.Drawing(unit=2)  # unit=2 makes elements have shorter than normal leads
d.push()
d += (R1 := elm.Resistor().down().label('20Ω'))
d += (V1 := elm.SourceV().down().reverse().label('120V'))
d += elm.Line().right().length(3)
d += elm.Dot()
d.pop()
d += elm.Line().right().length(3)
d += elm.Dot()
d += elm.SourceV().down().reverse().label('60V')
d += elm.Resistor().label('5Ω')
d += elm.Dot()
d += elm.LineDot().right().length(3)
d += elm.SourceI().up().label('36A')
d += elm.Resistor().label('10Ω')
d += elm.Dot()
d += elm.Line().left().length(3).hold()
d += elm.Line().right().length(3)
d += elm.Dot()
d += (R6 := elm.Resistor().down().toy(V1.end).label('6Ω'))
d += elm.Dot()
d += elm.Line().left().length(3).hold()
d += elm.Resistor().right().at(R6.start).label('1.6Ω')
d += elm.Dot().label('a')
d += elm.Line().right().at(R6.end)
d += elm.Dot().label('b')
d.draw()

Loop Currents

Using the schemdraw.elements.lines.LoopCurrent element to add loop currents, and rotating a label to make it fit.

../_images/analog_4_0.svg
d = schemdraw.Drawing(unit=5)
d += (V1 := elm.SourceV().label('20V'))
d += (R1 := elm.Resistor().right().label('400Ω'))
d += elm.Dot()
d.push()
d += (R2 := elm.Resistor().down().label('100Ω', loc='bot', rotate=True))
d += elm.Dot()
d.pop()
d += (L1 := elm.Line())
d += (I1 := elm.SourceI().down().label('1A', loc='bot'))
d += (L2 := elm.Line().left().tox(V1.start))
d.loopI([R1,R2,L2,V1], '$I_1$', pad=1.25)
d.loopI([R1,I1,L2,R2], '$I_2$', pad=1.25)  # Use R1 as top element for both so they get the same height
d.draw()

AC Loop Analysis

Another good problem for ECE students…

../_images/analog_5_0.svg
d = schemdraw.Drawing()
d += (I1 := elm.SourceI().label('5∠0° A'))
d += elm.Dot()
d.push()
d += elm.Capacitor().right().label('-j3Ω')
d += elm.Dot()
d.push()
d += elm.Inductor().down().label('j2Ω')
d += elm.Dot()
d.pop()
d += elm.Resistor().right().label('5Ω')
d += elm.Dot()
d += (V1 := elm.SourceV().down().reverse().label('5∠-90° V', loc='bot'))
d += elm.Line().left().tox(I1.start)
d.pop()
d += elm.Line().up().length(d.unit*.8)
d += (L1 := elm.Inductor().right().tox(V1.start).label('j3Ω'))
d += elm.Line().down().length(d.unit*.8)
d.labelI(L1, '$i_g$', top=False)
d.draw()

Infinite Transmission Line

Elements can be added inside for-loops if you need multiples. The ellipsis is just another circuit element, called DotDotDot since Ellipsis is a reserved keyword in Python. This also demonstrates the schemdraw.elements.ElementDrawing class to merge multiple elements into a single definition.

../_images/analog_6_0.svg
d1 = schemdraw.Drawing()
d1 += elm.Resistor()
d1.push()
d1 += elm.Capacitor().down()
d1 += elm.Line().left()
d1.pop()

d2 = schemdraw.Drawing()
for i in range(3):
    d2 += elm.ElementDrawing(d1)

d2.push()
d2 += elm.Line().length(d2.unit/6)
d2 += elm.DotDotDot()
d2 += elm.ElementDrawing(d1)
d2.pop()
d2.here = (d2.here[0], d2.here[1]-d2.unit)
d2 += elm.Line().right().length(d2.unit/6)
d2 += elm.DotDotDot()
d2.draw()

Power supply

Notice the diodes use the theta method to point them in the right directions. Also the use of newline characters inside resistor and capacitor labels.

../_images/analog_7_0.svg
d = schemdraw.Drawing(inches_per_unit=.5, unit=3)
d += (D1 := elm.Diode().theta(-45))
d += elm.Dot()
d += (D2 := elm.Diode().theta(225).reverse())
d += elm.Dot()
d += (D3 := elm.Diode().theta(135).reverse())
d += elm.Dot()
d += (D4 := elm.Diode().theta(45))
d += elm.Dot()

d += elm.Line().left().at(D3.start).length(d.unit*1.5)
d += elm.Dot(open=True)
d += (G := elm.Gap().up().toy(D1.start).label(['–', 'AC IN', '+']))
d += elm.Line().left().at(D4.end).tox(G.start)
d += elm.Dot(open=True)

d += (top := elm.Line().right().at(D2.start).length(d.unit*3))
d += (Q2 := elm.BjtNpn(circle=True).up().anchor('collector').label('Q2\n2n3055'))
d += elm.Line().down().at(Q2.base).length(d.unit/2)
d += (Q2b := elm.Dot())
d += elm.Line().left().length(d.unit/3)
d += (Q1 := elm.BjtNpn(circle=True).up().anchor('emitter').label('Q1\n    2n3054'))
d += elm.Line().up().at(Q1.collector).toy(top.center)
d += elm.Dot()

d += elm.Line().down().at(Q1.base).length(d.unit/2)
d += elm.Dot()
d += elm.Zener().down().reverse().label('D2\n500mA', loc='bot')
d += elm.Dot()
d += (G := elm.Ground())
d += elm.Line().left()
d += elm.Dot()
d += elm.Capacitor(polar=True).up().reverse().label('C2\n100$\mu$F\n50V', loc='bot')
d += elm.Dot()
d.push()
d += elm.Line().right()
d.pop()
d += elm.Resistor().up().toy(top.end).label('R1\n2.2K\n50V', loc='bot')
d += elm.Dot()

d.move(dx=-d.unit, dy=0)
d += elm.Dot()
d += elm.Capacitor(polar=True).down().toy(G.start).flip().label('C1\n 1000$\mu$F\n50V')
d += elm.Dot()
d += elm.Line().left().at(G.start).tox(D4.start)
d += elm.Line().up().toy(D4.start)

d += elm.Resistor().right().at(Q2b.center).label('R2').label('56$\Omega$ 1W', loc='bot')
d += elm.Dot()
d.push()
d += elm.Line().up().toy(top.start)
d += elm.Dot()
d += elm.Line().left().tox(Q2.emitter)
d.pop()
d += elm.Capacitor(polar=True).down().toy(G.start).label('C3\n470$\mu$F\n50V', loc='bot')
d += elm.Dot()
d += elm.Line().left().tox(G.start).hold()
d += elm.Line().right()
d += elm.Dot()
d += elm.Resistor().up().toy(top.center).label('R3\n10K\n1W', loc='bot')
d += elm.Dot()
d += elm.Line().left().hold()
d += elm.Line().right()
d += elm.Dot(open=True)
d += elm.Gap().down().toy(G.start).label(['+', '$V_{out}$', '–'])
d += elm.Dot(open=True)
d += elm.Line().left()
d.draw()