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Digital circuit symbols missing power/ground pins
All digital circuit diagram symbols in Circuit Wizard and Livewire do not have visible power or ground pins but instead take their power from a hidden digital power supply.
A separate hidden power supply is available for both TTL and CMOS digital components. The CMOS supply can vary between 3 and 15 volts whilst the TTL supply is fixed at 5 volts.
 
Changing the digital power supply
You can control and change the power supply for digital components via the Power Supply window.
To change the CMOS supply voltage in Circuit Wizard, select Power Supply... from the Project | Simulation menu.
To change the CMOS supply voltage in Livewire, select Power Supply... from the Tools | Simulation menu.
Nets are used to connect the power supply to the components. The CMOS power supply has the positive terminal connected to VDD and the negative to VSS. For TTL, the power supply has the positive terminal connected to VCC and the negative terminal to GND.
Adding terminals connected to any of these named nets allows you to access the hidden supply. This approach is recommended, particularly if the circuit is to be made into a PCB layout as all of the terminals will be connected to the appropriate supply rail.
For more information on this topic, click on the Help button in the Power Supply window.
 
 
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