Question

Arrange the following logic families in the order of increasing power dissipation : A. CMOS B. RTL C. TTL D. ECL Choose the correct answer from the options given below :

• A. D, B, C, A
• B. A, C, B, D
• C. D, C, B, A
• D. A, D, B, C

Hint:

Increasing power dissipation order: \[ \text{CMOS} < \text{TTL} < \text{RTL} < \text{ECL} \] CMOS has lowest power consumption while ECL has highest power dissipation.

Answer 1

The Correct Option is B

Concept: Different logic families consume different amounts of power. Power dissipation depends upon:
• Switching mechanism
• Biasing currents
• Operating speed
• Device structure General trend: \[ \text{CMOS} < \text{TTL} < \text{RTL} < \text{ECL} \] where:
• CMOS has minimum static power dissipation.
• ECL has maximum power dissipation because transistors never enter saturation.

Step 1: Analyze CMOS. CMOS uses complementary MOS transistors. Important feature:
• Almost zero static power dissipation. Thus CMOS has the lowest power consumption. Hence: \[ A \] comes first.

Step 2: Analyze TTL. TTL consumes more power than CMOS because:
• Bipolar transistors require bias current. However, TTL still dissipates less power than RTL. Hence: \[ C \] comes after CMOS.

Step 3: Analyze RTL. RTL uses resistor-transistor arrangements. Because of resistor current paths:
• Power dissipation becomes larger. Thus RTL consumes more power than TTL. Hence: \[ B \] comes next.

Step 4: Analyze ECL. ECL stands for: \[ \text{Emitter Coupled Logic} \] ECL has:
• Very high speed
• Continuous current flow
• No transistor saturation Due to continuous bias currents: \[ \text{Power dissipation is maximum} \] Hence: \[ D \] comes last.

Step 5: Write the final sequence. Therefore: \[ A,\ C,\ B,\ D \] Hence, the correct option is: \[ \boxed{(B)\ A,C,B,D} \]