What are the typical CMOS output levels at VDD = 5 V?

VOH(min) = 4.9 V and VOL(max) = 0.1 V

VOH(min) = 2.4 V and VOL(max) = 0.4 V

VOH(min) = 3.5 V and VOL(max) = 1.5 V

VOH(min) = 5.0 V and VOL(max) = 1.5 V

What are the CMOS input thresholds as fractions of VDD?

VIH(min) about 70% of VDD and VIL(max) about 30% of VDD

What are CMOS noise margins and how do they compare with TTL?

1.4 V each, much larger than TTL's 0.4 V

2078 Kartik · 3 marks

CMOS logic level profile

Short answer

For VDD=5V, output levels: VOH(min)=4.9V, VOL(max)=0.1V; input thresholds: VIH(min)=3.5V, VIL(max)=1.5V, giving noise margins of 1.4V. The output swings nearly rail-to-rail, and input thresholds are at 30% and 70% of VDD.

Draw the CMOS logic level profile for both input and output.

The CMOS logic level profile shows the voltage ranges for logic 0 and 1 at the output and at the input of a CMOS gate. Typical values for $V_{DD} = 5$ V:

  Output                 Input
 5.0 +--------+         5.0 +--------+
     | HIGH   |             | HIGH   |
 4.9 +--------+ VOH(min)    |        |
     |        |  NM_H=1.4   |        |
     |invalid |         3.5 +--------+ VIH(min)
     |        |             | indet. |
     |        |         1.5 +--------+ VIL(max)
     |        |  NM_L=1.4   | LOW    |
 0.1 +--------+ VOL(max)    |        |
     | LOW    |             |        |
 0.0 +--------+         0.0 +--------+

Output: $V_{OH(min)} = 4.9$ V, $V_{OL(max)} = 0.1$ V (nearly $V_{DD}$ and 0 V, since MOS outputs drive almost no DC current).
Input: $V_{IH(min)} = 3.5$ V (70% of $V_{DD}$ ), $V_{IL(max)} = 1.5$ V (30% of $V_{DD}$ ).
Noise margins: $NM_H = 4.9 - 3.5 = 1.4$ V and $NM_L = 1.5 - 0.1 = 1.4$ V, much larger than TTL's 0.4 V.

✓ Answer checked by Claude Opus 5.5 (high effort)

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