Digital Logic

Logic gate definitions are in the schemdraw.logic.logic module. Here it was imported with

from schemdraw import logic

Half Adder

Notice the half and full adders set the drawing unit to 0.5 so the lines aren’t quite as long and look better with logic gates.

with schemdraw.Drawing() as d:
    d.config(unit=0.5)
    S = logic.Xor().label('S', 'right')
    logic.Line().left(d.unit*2).at(S.in1).idot().label('A', 'left')
    B = logic.Line().left().at(S.in2).dot()
    logic.Line().left().label('B', 'left')
    logic.Line().down(d.unit*3).at(S.in1)
    C = logic.And().right().anchor('in1').label('C', 'right')
    logic.Wire('|-').at(B.end).to(C.in2)

Full Adder

with schemdraw.Drawing() as d:
    d.config(unit=0.5)
    X1 = logic.Xor()
    A = logic.Line().left(d.unit*2).at(X1.in1).idot().label('A', 'left')
    B = logic.Line().left().at(X1.in2).dot()
    logic.Line().left().label('B', 'left')

    logic.Line().right().at(X1.out).idot()
    X2 = logic.Xor().anchor('in1')
    C = logic.Line().down(d.unit*2).at(X2.in2)
    d.push()
    logic.Dot().at(C.center)
    logic.Line().tox(A.end).label('C$_{in}$', 'left')
    d.pop()

    A1 = logic.And().right().anchor('in1')
    logic.Wire('-|').at(A1.in2).to(X1.out)
    d.move_from(A1.in2, dy=-d.unit*2)
    A2 = logic.And().right().anchor('in1')
    logic.Wire('-|').at(A2.in1).to(A.start)
    logic.Wire('-|').at(A2.in2).to(B.end)
    d.move_from(A1.out, dy=-(A1.out.y-A2.out.y)/2)
    O1 = logic.Or().right().label('C$_{out}$', 'right')
    logic.Line().at(A1.out).toy(O1.in1)
    logic.Line().at(A2.out).toy(O1.in2)
    logic.Line().at(X2.out).tox(O1.out).label('S', 'right')

J-K Flip Flop

Note the use of the LaTeX command overline{Q} in the label to draw a bar over the inverting output label.

with schemdraw.Drawing() as d:
    # Two front gates (SR latch)
    G1 = logic.Nand(leadout=.75).anchor('in1')
    logic.Line().length(d.unit/2).label('Q', 'right')
    d.move_from(G1.in1, dy=-2.5)
    G2 = logic.Nand(leadout=.75).anchor('in1')
    logic.Line().length(d.unit/2).label(r'$\overline{Q}$', 'right')
    logic.Wire('N', k=.5).at(G2.in1).to(G1.out).dot()
    logic.Wire('N', k=.5).at(G1.in2).to(G2.out).dot()

    # Two back gates
    logic.Line().left(d.unit/6).at(G1.in1)
    J = logic.Nand(inputs=3).anchor('out').right()
    logic.Wire('n', k=.5).at(J.in1).to(G2.out, dx=1).dot()
    logic.Line().left(d.unit/4).at(J.in2).label('J', 'left')
    logic.Line().left(d.unit/6).at(G2.in2)
    K = logic.Nand(inputs=3).right().anchor('out')
    logic.Wire('n', k=-.5).at(K.in3).to(G1.out, dx=.5).dot()
    logic.Line().left(d.unit/4).at(K.in2).label('K', 'left')
    C = logic.Line().at(J.in3).toy(K.in1)
    logic.Dot().at(C.center)
    logic.Line().left(d.unit/4).label('CLK', 'left')

S-R Latch (Gates)

with schemdraw.Drawing() as d:
    g1 = logic.Nor()
    d.move_from(g1.in1, dy=-2.5)
    g2 = logic.Nor().anchor('in1')
    g1out = logic.Line().right(.25).at(g1.out)
    logic.Wire('N', k=.5).at(g2.in1).to(g1out.end).dot()
    g2out = logic.Line().right(.25).at(g2.out)
    logic.Wire('N', k=.5).at(g1.in2).to(g2out.end).dot()
    logic.Line().at(g1.in1).left(.5).label('R', 'left')
    logic.Line().at(g2.in2).left(.5).label('S', 'left')
    logic.Line().at(g1.out).right(.75).label('Q', 'right')
    logic.Line().at(g2.out).right(.75).label(r'$\overline{Q}$', 'right')