IC powered via Zener Diode

Discussion in 'The Projects Forum' started by cenee, May 20, 2014.

  1. cenee

    Thread Starter Member

    Apr 20, 2006
    Hi. I have this circuit where most of it is powered by 9V, but I am using a 5V chip that I am planning to power via a 5V Zener diode.
    The IC unit, which gets a signal from the 9V circuit via a voltage divider (to 5V), gives also an output signal that goes to an AND Gate in the 9V circuit ......
    My question is: how reliable will the Zener Diode be/works when powering an IC unit? Anyone has used a Zener to powered an IC ?

    -already know that a 7805 would do the job
    -IC Max power=0.45W --> Rz=(9-5)/0.09=44 Ohm
    -Any comments about the 9V to 5V interaction?
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    The zener should be good and the divider to the 5 volt chip ok. You may have some problem with the 5 volt signal to the cmos ic. Look to see what the switch voltage is on the cmos part and how close to 5 volts the output of the 5 volt part goes. It may not go high enough.
  3. crutschow


    Mar 14, 2008
    A zener wastes some current as it requires current to operate in addition to the IC current. An LM117 or similar series regulator would be better for that.

    Note that the zener is shown upside down in your circuit diagram. The zener operates in reverse biased breakdown so the anode must go to ground.