Each transistor has a (red) heat port and a (green) substrate node. The heat port uses a different color embracing the philosophy of Modelica libraries, which distinguish different connectors by color to make it visibly unlikely that impossible connections are being made by the user. The substrate node is an electrical node and should therefore be drawn in blue. However, we decided to use a different color to prevent the circuit from becoming unreadable due to an abundance of connections.
All internal heat ports need to be tied to the external heat port. All internal substrate nodes need to be tied to the lowest voltage, i.e., the external Vee port.
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