Integrated-Circuit Logic Families - Technical MCQs

Q1:

Whenever a totem-pole TTL output goes from LOW to HIGH, a high-amplitude current spike is drawn from the Vcc supply. How is this effect corrected to a digital circuit?

A By connecting a radio-frequency capacitor from Vcc to ground.

B By using a switching power supply

C By connecting a capacitor from Vout to ground

D By connecting a large resistor from Vcc to Vout

ANS:A - By connecting a radio-frequency capacitor from Vcc to ground.

The most common technique uses small radio frequency capacitors connected from Vcc to ground essentially to short out these high-frequency spikes. This is called power-supply decoupling. The capacitor values are from 0.01micro farad to 0.1mcro farad.