The AND gate is a digital logic circuit fragment where the output is low unless all inputs are high. With all inputs high, the  output will be high.

This page will be demonstrating the AND gate circuit basics using:

  • Switches:
  • NPN BJTs:
  • SN74HC08N Quad 2 input positive AND gates IC:

Digital (on or off) signals:

  • On/High signal will indicate a point in the circuit that is at about 5V.
  • Off/Low signal will indicate a point in the circuit that is at about 0V.

Video below: Transistor circuit 7 AND gate switches 2N2222 NPN BJT and SN74HC08N quad 2 input pos AND gates Click here to watch directly on YouTube!

Diagram covering the basics of making an electronics AND gate with mechanical switches or NPN Bipolar Junction Transistors BJTs or by using a SN74HC08N Quadruple 2 Input Positive AND Gates
Diagram covering the basics of making an electronics AND gate with mechanical switches or NPN Bipolar Junction Transistors BJTs or by using a SN74HC08N Quadruple 2 Input Positive AND Gates

Switch based AND gate:

If single pole-single throw or push-button switches are connected in series, then a series load will only be on if all series switches are in the on position.

Bipolar Junction Transistor BJT based AND gate:

Connecting NPN BJT emitters and collectors in series with a load will only allow the load to be on if there is enough positive voltage/current given to the base of all transistors to cause saturation.

SN74HC08N IC based AND gate:

Logic gate integrated circuits usually have multiple built in logic gates where you only have to apply a signal to the input pins to control whether the output is high or low. They will probably be susceptible to static shock and only be able to handle low power loads directly, so use care when handling and use a proper transistor controlled by the gate output pin for loads larger than the IC can handle. Consult the component datasheet to find it’s particular parameters.

This is a new page, which will be updated soon!


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