I am experimenting with basic logic gates on multisim. From my understanding in digital logic the 0/1 represent output voltages of 3.3 - 5 and 0 V. My logic gate pictured conducts a current when 5 V is applied to the base terminals but nowhere in the output do I measure a voltage in the high range and the output of an AND gate should have 3.3/5 volts on it when high if I am not mistaken. Is the current just converted to a voltage or did I connect something incorrectly here. Thank you guys.enter image description here

  • \$\begingroup\$ The transistor measures base voltage compared to its emitter. This means if the base is 5 volts but the emitter is also 5 volts, the transistor is off because the base-emitter voltage that would turn it on is actually 0 volts. \$\endgroup\$
    – user253751
    Jul 16, 2023 at 21:21

1 Answer 1


This circuit (and many others in introductory texts) is not an AND gate that can be combined with other gates of the same type.

For some of the simplest such circuits, check out 1960s-era RTL logic. For example, the RTL Cookbook from Donald Lancaster (RIP). He used somewhat unconventional symbols by modern standards.

For example, this 2-input NOR gate:

enter image description here

You can add an inverter to each input and get a positive-logic AND gate.

  • 1
    \$\begingroup\$ Thanks for the link, I used that book for many years. \$\endgroup\$
    – Gil
    Jul 16, 2023 at 4:24
  • \$\begingroup\$ I'd add that in my opinion at least, basic familiarity with RTL and DTL is valuable since it makes it far easier to understand how early computers etc. were built with what would appear to be a ridiculously low number of active components. \$\endgroup\$ Jul 16, 2023 at 15:32

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