adding C4 symbol and schematic
diff --git a/xschem/C4.sch b/xschem/C4.sch
new file mode 100644
index 0000000..01150c1
--- /dev/null
+++ b/xschem/C4.sch
@@ -0,0 +1,133 @@
+v {xschem version=3.0.0 file_version=1.2 }
+G {}
+K {}
+V {}
+S {}
+E {}
+N 130 -260 130 -190 {
+lab=#net1}
+N 80 -190 130 -190 {
+lab=#net1}
+N 250 -200 250 -190 {
+lab=#net1}
+N 130 -190 250 -190 {
+lab=#net1}
+N 250 -270 250 -260 {
+lab=#net1}
+N 250 -300 250 -270 {
+lab=#net1}
+N 250 -200 250 -150 {
+lab=#net1}
+N 250 -90 250 -50 {
+lab=#net2}
+N 130 -340 130 -320 {
+lab=#net3}
+N 250 -380 250 -360 {
+lab=#net3}
+N 430 -160 430 -120 {
+lab=#net2}
+N 250 -190 390 -190 {
+lab=#net1}
+N 430 -190 450 -190 {
+lab=#net2}
+N 450 -190 450 -150 {
+lab=#net2}
+N 430 -150 450 -150 {
+lab=#net2}
+N 230 -120 250 -120 {
+lab=#net2}
+N 230 -120 230 -80 {
+lab=#net2}
+N 230 -80 250 -80 {
+lab=#net2}
+N 220 -330 250 -330 {
+lab=GND}
+N 430 -360 430 -220 {
+lab=vout}
+N 430 -460 430 -420 {
+lab=#net3}
+N 430 -390 460 -390 {
+lab=#net3}
+N 460 -440 460 -390 {
+lab=#net3}
+N 430 -440 460 -440 {
+lab=#net3}
+N 290 -330 430 -330 {
+lab=vout}
+N 370 -390 390 -390 {
+lab=vth}
+N 430 -330 640 -330 {
+lab=vout}
+N 290 -120 320 -120 {
+lab=vtl}
+N -20 -190 20 -190 {
+lab=vin}
+N 250 -260 250 -190 {
+lab=#net1}
+N -110 -480 -90 -480 {
+lab=vin}
+N -110 -540 -90 -540 {
+lab=vth}
+N -110 -510 -90 -510 {
+lab=vtl}
+N -120 -450 -100 -450 {
+lab=vout}
+N 430 -120 430 -50 {
+lab=#net2}
+N 250 -50 430 -50 {
+lab=#net2}
+N 340 -50 340 -10 {
+lab=#net2}
+N 250 -530 250 -380 {
+lab=#net3}
+N 250 -460 430 -460 {
+lab=#net3}
+N 130 -460 250 -460 {
+lab=#net3}
+N 130 -460 130 -340 {
+lab=#net3}
+N 20 -190 80 -190 {}
+N 130 -330 130 -260 {}
+C {sky130_fd_pr/nfet_01v8.sym} 270 -120 0 1 {name=M3
+L=0.15
+W=1
+nf=1 mult=1
+model=nfet_01v8
+spiceprefix=X
+}
+C {sky130_fd_pr/nfet_01v8.sym} 270 -330 0 1 {name=M4
+L=0.15
+W=1
+nf=1 mult=1
+model=nfet_01v8
+spiceprefix=X
+}
+C {sky130_fd_pr/nfet_01v8.sym} 410 -190 0 0 {name=M5
+L=0.15
+W=1
+nf=1 mult=1
+model=nfet_01v8
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_01v8.sym} 410 -390 0 0 {name=M11
+L=0.15
+W=1
+nf=1 mult=1
+model=pfet_01v8
+spiceprefix=X
+}
+C {devices/lab_pin.sym} 220 -330 0 0 {name=l7 sig_type=std_logic lab=GND}
+C {devices/lab_pin.sym} 370 -390 0 0 {name=l10 sig_type=std_logic lab=vth}
+C {devices/lab_pin.sym} 320 -120 0 1 {name=l11 sig_type=std_logic lab=vtl}
+C {devices/lab_pin.sym} -20 -190 0 0 {name=l12 sig_type=std_logic lab=vin}
+C {devices/lab_pin.sym} 640 -330 0 1 {name=l13 sig_type=std_logic lab=vout}
+C {devices/ipin.sym} -100 -540 0 0 {name=p1 lab=vth}
+C {devices/ipin.sym} -100 -510 0 0 {name=p2 lab=vtl}
+C {devices/ipin.sym} -100 -480 0 0 {name=p3 lab=vin}
+C {devices/opin.sym} -110 -450 0 0 {name=p4 lab=vout}
+C {devices/lab_pin.sym} -90 -540 0 1 {name=l8 sig_type=std_logic lab=vth}
+C {devices/lab_pin.sym} -90 -510 0 1 {name=l9 sig_type=std_logic lab=vtl}
+C {devices/lab_pin.sym} -90 -480 0 1 {name=l14 sig_type=std_logic lab=vin}
+C {devices/lab_pin.sym} -120 -450 0 0 {name=l15 sig_type=std_logic lab=vout}
+C {devices/iopin.sym} 330 -10 0 0 {name=p5 lab=vss}
+C {devices/iopin.sym} 240 -530 0 0 {name=p6 lab=vdda}
diff --git a/xschem/C4.sym b/xschem/C4.sym
new file mode 100644
index 0000000..6e000c9
--- /dev/null
+++ b/xschem/C4.sym
@@ -0,0 +1,33 @@
+v {xschem version=3.0.0 file_version=1.2 }
+G {}
+K {type=subcircuit
+format="@name @pinlist @symname"
+template="name=x1"
+}
+V {}
+S {}
+E {}
+L 4 -130 -30 130 -30 {}
+L 4 -130 30 130 30 {}
+L 4 -130 -30 -130 30 {}
+L 4 130 -30 130 30 {}
+L 4 -150 -20 -130 -20 {}
+L 4 -150 0 -130 0 {}
+L 4 -150 20 -130 20 {}
+L 4 130 0 150 0 {}
+L 7 0 -50 0 -30 {}
+L 7 0 30 0 50 {}
+B 5 -152.5 -22.5 -147.5 -17.5 {name=vth dir=in }
+B 5 -2.5 -52.5 2.5 -47.5 {name=vdda dir=inout }
+B 5 -152.5 -2.5 -147.5 2.5 {name=vtl dir=in }
+B 5 -152.5 17.5 -147.5 22.5 {name=vin dir=in }
+B 5 147.5 -2.5 152.5 2.5 {name=vout dir=out }
+B 5 -2.5 47.5 2.5 52.5 {name=vss dir=inout }
+T {@symname} -27 -6 0 0 0.3 0.3 {}
+T {@name} 135 -42 0 0 0.2 0.2 {}
+T {vth} -125 -24 0 0 0.2 0.2 {}
+T {vdda} 15 -24 0 1 0.2 0.2 {}
+T {vtl} -125 -4 0 0 0.2 0.2 {}
+T {vin} -125 16 0 0 0.2 0.2 {}
+T {vout} 125 -4 0 1 0.2 0.2 {}
+T {vss} 5 16 0 1 0.2 0.2 {}
