will having diode on Vcc increase power consumption
Not as such, because of the volts drop the consumption will be reduced from the device but this drop will be dissipated in the diode. So back to square one.
will having diode on Vcc increase power consumption
Not as such, because of the volts drop the consumption will be reduced from the device but this drop will be dissipated in the diode. So back to square one.