{"id":1599,"date":"2026-01-07T02:41:48","date_gmt":"2026-01-07T00:41:48","guid":{"rendered":"https:\/\/blog.the-leviathan.ch\/?p=1599"},"modified":"2026-01-07T02:41:48","modified_gmt":"2026-01-07T00:41:48","slug":"librepdk-auto-generator-driver-circuit","status":"publish","type":"post","link":"https:\/\/blog.the-leviathan.ch\/?p=1599","title":{"rendered":"LibrePDK auto generator: Driver Circuit"},"content":{"rendered":"\n

After fighting with the place and route part of LibrePDK for over a month now, I finally managed to turn a Qucs schematic like this one into a JSON netlist which then can be fed to the generator, placer and detailed router.<\/p>\n\n\n\n

The schematics below which has been drawn in Qucs, can be found in the LibrePDK GitLab repo<\/a> and shows a driver with an input, output and enable signal.<\/p>\n\n\n

\n
\"\"<\/a><\/figure>\n<\/div>\n\n\n

Converting the netlist into JSON results in the file which can be found in the GitLab repo as well<\/a><\/p>\n\n\n\n

It’s 8 transistors with M7\/M8 being the output stage which have to drive all the current and hence need a muss lower on resistance respectively saturation current.<\/p>\n\n\n\n

{\n\t\"name\": \"driver_circuit\",\n\t\"nets\": [\"VDD\",\"VSS\",\"EN\",\"IN\",\"OUT\"],\n\t\"instances\": {\n\t\t\"M1\": {\n\t\t\t\"type\":\"pmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"3\",\n\t\t\t\t\"gate\": \"EN\",\n\t\t\t\t\"source\": \"4\",\n\t\t\t\t\"bulk\": \"4\"\n\t\t\t},\n\t\t\t\"R_on\": 1000.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M2\": {\n\t\t\t\"type\":\"pmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"1\",\n\t\t\t\t\"gate\": \"EN\",\n\t\t\t\t\"source\": \"VDD\",\n\t\t\t\t\"bulk\": \"VDD\"\n\t\t\t},\n\t\t\t\"R_on\": 1000.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M3\": {\n\t\t\t\"type\":\"nmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"3\",\n\t\t\t\t\"gate\": \"1\",\n\t\t\t\t\"source\": \"2\",\n\t\t\t\t\"bulk\": \"2\"\n\t\t\t},\n\t\t\t\"R_on\": 1000.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M4\": {\n\t\t\t\"type\":\"nmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"2\",\n\t\t\t\t\"gate\": \"IN\",\n\t\t\t\t\"source\": \"VSS\",\n\t\t\t\t\"bulk\": \"VSS\"\n\t\t\t},\n\t\t\t\"R_on\": 1900.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M5\": {\n\t\t\t\"type\":\"pmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"4\",\n\t\t\t\t\"gate\": \"IN\",\n\t\t\t\t\"source\": \"VDD\",\n\t\t\t\t\"bulk\": \"VDD\"\n\t\t\t},\n\t\t\t\"R_on\": 1000.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M6\": {\n\t\t\t\"type\":\"nmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"1\",\n\t\t\t\t\"gate\": \"EN\",\n\t\t\t\t\"source\": \"VSS\",\n\t\t\t\t\"bulk\": \"VSS\"\n\t\t\t},\n\t\t\t\"R_on\": 1000.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M7\": {\n\t\t\t\"type\":\"pmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"OUT\",\n\t\t\t\t\"gate\": \"3\",\n\t\t\t\t\"source\": \"VDD\",\n\t\t\t\t\"bulk\": \"VDD\"\n\t\t\t},\n\t\t\t\"R_on\": 100.0,\n\t\t\t\"V_DS\": 1.2\n\t\t},\n\t\t\"M8\": {\n\t\t\t\"type\":\"nmos\",\n\t\t\t\"nets\": {\n\t\t\t\t\"drain\": \"OUT\",\n\t\t\t\t\"gate\": \"3\",\n\t\t\t\t\"source\": \"VSS\",\n\t\t\t\t\"bulk\": \"VSS\"\n\t\t\t},\n\t\t\t\"R_on\": 100.0,\n\t\t\t\"V_DS\": 1.2\n\t\t}\n\t}\n}<\/code><\/pre>\n\n\n\n
Lets say we’ve cloned the repo with<\/p>\n\n\n\n
git clone https:\/\/gitlab.libresilicon.com\/generator-tools\/librepdk.git\ncd librepdk\nexport LIBREPDK_REPO=`pwd`<\/code><\/pre>\n\n\n\n
Running that JSON file through LibrePDK with the command below leaves us not only with a GDSII but also a SPICE model, Magic VLSI, DEF and LEF file.<\/p>\n\n\n\n
export DESIGN_DIR=$LIBREPDK_REPO\/tests\/driver_circuit\nexport DESIGN_FILE=$DESIGN_DIR\/driver_circuit.json\nexport ANAROUTE_WORKDIR=$LIBREPDK_REPO\/workdir_driver\nexport ANAROUTE_DEBUG_OUT=$ANAROUTE_WORKDIR\/debug\/\nexport ANAROUTE_DEBUG_OUT_PREFIX=$ANAROUTE_DEBUG_OUT\/snapshot\n\nrm -rf $ANAROUTE_WORKDIR\nmkdir -p $ANAROUTE_DEBUG_OUT\npushd $ANAROUTE_WORKDIR\nuv run ..\/bin\/librepdk_generator -d $DESIGN_FILE -t SG13G2 -o out &> out.log\ncp $DESIGN_DIR\/*.spice .\npopd<\/code><\/pre>\n\n\n\n
First lets look at the GDS2 file. We can easily identify M7 and M8 because they’re much larger than the other transistors and have fingers.<\/p>\n\n\n
\n
\"\"<\/a><\/figure>\n<\/div>\n\n\n
Running the test simulations in NG Spice for when the input is enabled and disabled results in the desired behavior.<\/p>\n\n\n\n
Output enable is inverted so when it’s 1 (VDD) the output is disabled, when it’s 0 (VSS), the output is enabled.<\/p>\n\n\n\n
The below NGSPice simulation shows the result of running `ngspice workdir_driver\/test1.spice<\/code> with the output being disabled.<\/p>\n\n\n
\n
\"\"<\/a><\/figure>\n<\/div>\n\n\n
The below NGSPice simulation shows the result of running `ngspice workdir_driver\/test2.spice<\/code> with the output being enabled.<\/p>\n\n\n
\n
\"\"<\/a><\/figure>\n<\/div>","protected":false},"excerpt":{"rendered":"
After fighting with the place and route part of LibrePDK for over a month now, I finally managed to turn a Qucs schematic like this one into a JSON netlist which then can be fed to the generator, placer and detailed router. The schematics below which has been drawn in Qucs, can be found in … Continue reading LibrePDK auto generator: Driver Circuit<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1599","post","type-post","status-publish","format-standard","hentry","category-daily"],"_links":{"self":[{"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/posts\/1599","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1599"}],"version-history":[{"count":4,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/posts\/1599\/revisions"}],"predecessor-version":[{"id":1607,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=\/wp\/v2\/posts\/1599\/revisions\/1607"}],"wp:attachment":[{"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1599"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1599"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.the-leviathan.ch\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}