Add test bench
diff --git a/xschem/tb_BGR_pvt_lvs.sch b/xschem/tb_BGR_pvt_lvs.sch
new file mode 100644
index 0000000..76b695c
--- /dev/null
+++ b/xschem/tb_BGR_pvt_lvs.sch
@@ -0,0 +1,123 @@
+v {xschem version=3.0.0 file_version=1.2 }
+G {}
+K {}
+V {}
+S {}
+E {}
+N 140 -160 180 -160 {
+lab=porst}
+N 320 -310 350 -310 {
+lab=Vbg}
+N 450 -380 490 -380 {
+lab=#net1}
+N 440 -380 450 -380 {
+lab=#net1}
+N 440 -450 440 -380 {
+lab=#net1}
+N 440 -450 450 -450 {
+lab=#net1}
+N 490 -450 550 -450 {
+lab=VDD}
+N 550 -510 550 -450 {
+lab=VDD}
+N 490 -510 550 -510 {
+lab=VDD}
+N 490 -390 490 -380 {
+lab=#net1}
+N 490 -420 490 -390 {
+lab=#net1}
+N 490 -510 490 -480 {
+lab=VDD}
+N 490 -320 490 -290 {
+lab=#net2}
+N 320 -280 350 -280 {
+lab=#net2}
+N 320 -270 350 -270 {
+lab=#net3}
+N 320 -260 350 -260 {
+lab=#net4}
+N 320 -250 350 -250 {
+lab=#net5}
+N 320 -240 350 -240 {
+lab=#net6}
+N 320 -230 350 -230 {
+lab=#net7}
+N 350 -280 490 -280 {
+lab=#net2}
+N 490 -290 490 -280 {
+lab=#net2}
+N 320 -290 350 -290 {
+lab=#net8}
+C {devices/code.sym} 640 -260 0 0 {name=TT_MODELS
+only_toplevel=true
+format="tcleval( @value )"
+value="
+** opencircuitdesign pdks install
+.lib $::SKYWATER_MODELS/sky130.lib.spice tt
+
+"
+spice_ignore=false}
+C {devices/vsource.sym} 830 -210 0 0 {name=V1 net_name=true
+*value="'VDD' pwl 0us 0 1us 'VDD'"
+value=1.8}
+C {devices/vdd.sym} 830 -240 0 0 {name=l9 lab=VDD}
+C {devices/gnd.sym} 830 -180 0 0 {name=l22 lab=GND}
+C {devices/vsource.sym} 830 -100 0 0 {name=V2 net_name=true value="0 pulse(0V 1.8V 10us 0us 0us 5us)"}
+C {devices/gnd.sym} 830 -70 0 0 {name=l12 lab=GND}
+C {devices/lab_pin.sym} 830 -130 0 0 {name=l23 lab=porst}
+C {devices/code_shown.sym} -240 -570 0 0 {name=NGSPICE3
+only_toplevel=true
+spice_ignore=false
+value="
+.option savecurrents
+.option warn=1
+.dc temp -20 100 1
+.control
+save all
+
+run
+plot Vbg
+plot deriv(Vbg)
+
+
+plot vm1#branch
+plot deriv(vm1#branch)
+
+
+save vbg deriv(vbg)
+
+
+
+
+unset askquit
+*quit
+.endc
+" }
+C {devices/gnd.sym} 230 -60 0 0 {name=l2 lab=GND}
+C {devices/lab_pin.sym} 140 -160 0 0 {name=l3 lab=porst}
+C {devices/lab_pin.sym} 350 -310 0 1 {name=l4 lab=Vbg}
+C {sky130_fd_pr/pfet_01v8_lvt.sym} 470 -450 0 0 {name=M19
+L=1
+W=1
+nf=1
+mult=5
+ad="'int((nf+1)/2) * W/nf * 0.29'"
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/2) * W/nf * 0.29'"
+ps="'2*int((nf+2)/2) * (W/nf + 0.29)'"
+nrd="'0.29 / W'" nrs="'0.29 / W'"
+sa=0 sb=0 sd=0
+model=pfet_01v8_lvt
+spiceprefix=X
+}
+C {devices/vdd.sym} 490 -510 0 0 {name=l7 lab=VDD}
+C {devices/ammeter.sym} 490 -350 0 0 {name=Vm1 current=40e-6}
+C {noconn.sym} 340 -310 1 0 {name=l8}
+C {devices/vdd.sym} 230 -340 0 0 {name=l1 lab=VDD}
+C {noconn.sym} 350 -270 2 0 {name=l5}
+C {noconn.sym} 350 -260 2 0 {name=l6}
+C {noconn.sym} 350 -250 2 0 {name=l10}
+C {noconn.sym} 350 -240 2 0 {name=l11}
+C {noconn.sym} 350 -230 2 0 {name=l13}
+C {noconn.sym} 350 -290 2 0 {name=l14}
+C {BGR_lvs.sym} 10 -40 0 0 {name=X1}
diff --git a/xschem/tb_BGR_tran_lvs.sch b/xschem/tb_BGR_tran_lvs.sch
new file mode 100644
index 0000000..b28476c
--- /dev/null
+++ b/xschem/tb_BGR_tran_lvs.sch
@@ -0,0 +1,112 @@
+v {xschem version=3.0.0 file_version=1.2 }
+G {}
+K {}
+V {}
+S {}
+E {}
+N 140 -160 180 -160 {
+lab=porst}
+N 320 -310 350 -310 {
+lab=Vbg}
+N 450 -380 490 -380 {
+lab=#net1}
+N 440 -380 450 -380 {
+lab=#net1}
+N 440 -450 440 -380 {
+lab=#net1}
+N 440 -450 450 -450 {
+lab=#net1}
+N 490 -450 550 -450 {
+lab=VDD}
+N 550 -510 550 -450 {
+lab=VDD}
+N 490 -510 550 -510 {
+lab=VDD}
+N 490 -390 490 -380 {
+lab=#net1}
+N 490 -420 490 -390 {
+lab=#net1}
+N 490 -510 490 -480 {
+lab=VDD}
+N 320 -290 490 -290 {
+lab=#net2}
+N 490 -320 490 -290 {
+lab=#net2}
+N 320 -280 350 -280 {
+lab=#net3}
+N 320 -270 350 -270 {
+lab=#net4}
+N 320 -260 350 -260 {
+lab=#net5}
+N 320 -250 350 -250 {
+lab=#net6}
+N 320 -240 350 -240 {
+lab=#net7}
+N 320 -230 350 -230 {
+lab=#net8}
+C {devices/code.sym} 640 -260 0 0 {name=TT_MODELS
+only_toplevel=true
+format="tcleval( @value )"
+value="
+** opencircuitdesign pdks install
+.lib $::SKYWATER_MODELS/sky130.lib.spice tt
+
+"
+spice_ignore=false}
+C {devices/vsource.sym} 830 -210 0 0 {name=V1 net_name=true
+value="'VDD' pwl 0us 0 1us 'VDD'"
+*value=1.8}
+C {devices/vdd.sym} 830 -240 0 0 {name=l9 lab=VDD}
+C {devices/gnd.sym} 830 -180 0 0 {name=l22 lab=GND}
+C {devices/vsource.sym} 830 -100 0 0 {name=V2 net_name=true value="0 pulse(0V 1.8V 10us 0us 0us 5us)"}
+C {devices/gnd.sym} 830 -70 0 0 {name=l12 lab=GND}
+C {devices/lab_pin.sym} 830 -130 0 0 {name=l23 lab=porst}
+C {devices/gnd.sym} 230 -60 0 0 {name=l2 lab=GND}
+C {devices/lab_pin.sym} 140 -160 0 0 {name=l3 lab=porst}
+C {devices/lab_pin.sym} 350 -310 0 1 {name=l4 lab=Vbg}
+C {noconn.sym} 350 -280 0 1 {name=l5}
+C {noconn.sym} 350 -270 0 1 {name=l6}
+C {sky130_fd_pr/pfet_01v8_lvt.sym} 470 -450 0 0 {name=M19
+L=1
+W=1
+nf=1
+mult=5
+ad="'int((nf+1)/2) * W/nf * 0.29'"
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/2) * W/nf * 0.29'"
+ps="'2*int((nf+2)/2) * (W/nf + 0.29)'"
+nrd="'0.29 / W'" nrs="'0.29 / W'"
+sa=0 sb=0 sd=0
+model=pfet_01v8_lvt
+spiceprefix=X
+}
+C {devices/vdd.sym} 490 -510 0 0 {name=l7 lab=VDD}
+C {devices/ammeter.sym} 490 -350 0 0 {name=Vm1 current=40e-6}
+C {noconn.sym} 340 -310 1 0 {name=l8}
+C {devices/code_shown.sym} -180 -410 0 0 {name=s2
+only_toplevel=true
+spice_ignore=false
+
+value="
+.option savecurrents
+
+.param VDD=1.8
+.control
+save all
+
+run
+option temp=27
+tran 0.1n 20u
+plot VDD Vbg porst
+plot v.x1.vm5#branch
+
+unset askquit
+
+.endc
+"}
+C {noconn.sym} 350 -260 0 1 {name=l10}
+C {noconn.sym} 350 -250 0 1 {name=l11}
+C {noconn.sym} 350 -240 0 1 {name=l13}
+C {noconn.sym} 350 -230 0 1 {name=l14}
+C {devices/vdd.sym} 230 -340 0 0 {name=l1 lab=VDD}
+C {BGR_lvs.sym} 10 -40 0 0 {name=X1}
