Digital Electronics-Integrated-CircuitLogic Families
Digital Electronics-Integrated-CircuitLogic Families
1. Which of the following logic families has the highest maximum clock frequency?
- S-TTL
- AS-TTL
- HS-TTL
- HCMOS
2. Why is the fan-out of CMOS gates frequency dependent?
- Each CMOS input gate has a specific propagation time and this limits the number of different gates that can be connected to the output of a CMOS gate.
- When the frequency reaches the critical value, the gate will only be capable of delivering 70% of the normal output voltage and consequently the output power will be one-half of normal; this defines the upper operating frequency.
- The higher the number of gates attached to the output, the more frequently they will have to be serviced, thus reducing the frequency at which each will be serviced with an input signal.
- The input gates of the FETs are predominantly capacitive, and as the signal frequency increases the capacitive loading also increases, thereby limiting the number of loads that may be attached to the output of the driving gate.
3. Logic circuits that are designated as buffers, drivers, or buffer/drivers are designed to have:
- a greater current/voltage capability than an ordinary logic circuit.
- greater input current/voltage capability than an ordinary logic circuit.
- a smaller output current/voltage capability than an ordinary logic.
- greater input and output current/voltage capability than an ordinary logic circuit.
4. Which of the following will not normally be found on a data sheet?
- Minimum HIGH level output voltage
- Maximum LOW level output voltage
- Minimum LOW level output voltage
- Maximum HIGH level input current
5. Which of the following logic families has the shortest propagation delay?
- S-TTL
- AS-TTL
- HS-TTL
- HCMOS
6. Which of the following summarizes the important features of ECL?
- Low noise margin, low output voltage swing, negative voltage operation, fast, and high power consumption
- Good noise immunity, negative logic, high frequency capability, low power dissipation, and short propagation time
- Slow propagation time, high frequency response, low power consumption, and high output voltage swings
- Poor noise immunity, positive supply voltage operation, good low frequency operation, and low power
7. What must be done to interface TTL to CMOS?
- A dropping resistor must be used on the CMOS 12 V supply to reduce it to 5 V for the TTL.
- As long as the CMOS supply voltage is 5 V, they can be interfaced; however, the fan-out of the TTL is limited to five CMOS gates.
- A 5 V Zener diode must be placed across the inputs of the TTL gates in order to protect them from the higher output voltages of the CMOS gates.
- A pull-up resistor must be used between the TTL output-CMOS input node and Vcc; the value of RP will depend on the number of CMOS gates connected to the node.
8. What causes low-power Schottky TTL to use less power than the 74XX series TTL?
- The Schottky-clamped transistor
- Nothing. The 74XX series uses less power.
- A larger value resistor
- Using NAND gates
9. What are the major differences between the 5400 and 7400 series of ICs?
- The 5400 series are military grade and require tighter supply voltages and temperatures.
- The 5400 series are military grade and allow for a wider range of supply voltages and temperatures.
- The 7400 series are an improvement over the original 5400s.
- The 7400 series was originally developed by Texas Instruments. The 5400 series was brought out by National Semiconductors after TI's patents expired, as a second supply source.
10. Which of the following statements apply to CMOS devices?
- The devices should not be inserted into circuits with the power on.
- All tools, test equipment, and metal workbenches should be tied to earth ground.
- The devices should be stored and shipped in antistatic tubes or conductive foam.
- All of the above.