This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN7404: Schematic has unrecognised symbols

Part Number: SN7404

On page 4 of the data sheet there are schematics for each gate in the chip.  The LS04 and S04 schematics include a symbol that looks like a BJT transistor, but the "base" component has what looks like  Zenner symbol attached.

Please advise what this means or how it is referenced.

Rgds br

  • Hello,

    The symbol you are referring to is called a Schottky transistor. Its equivalent circuit is shown below:

    This design prevents the transistor from saturating allowing for a faster switching speed.

    The voltage drop across the diode of .3V plus the voltage drop across the transistor of .2V gives a .5V base-emitter voltage, Since this .5V is less than the .8V required for the transistor to go into saturation, the Schottky transistor never goes into saturation. BJT's take a long time switch out of the saturation region and so if they cannot be in the saturation region, they are able to switch much faster.