555 timer output levels with VCC = +10 V (bipolar 555) Estimate the typical HIGH and LOW output voltages of a standard bipolar 555 timer powered from +10 V under moderate load.

Introduction / Context:
The bipolar NE555 output stage uses bipolar transistors that cannot swing exactly to the rails under load. Consequently, the HIGH level is typically below VCC by about 1.2 V to 1.7 V, and the LOW level is a small saturation voltage above ground. This question checks recognition of realistic 555 output levels versus ideal rail-to-rail assumptions.

Given Data / Assumptions:

• Standard bipolar 555 (not CMOS 555), VCC = +10 V.
• Moderate load conditions typical of datasheets.
• Expect VOH somewhat less than VCC and VOL near ground.

Concept / Approach:
Because the bipolar totem-pole cannot reach the rails, VOH ≈ VCC − about 1.5 V. VOL is on the order of a few hundred millivolts. These typical values align with many datasheet examples given specified sink or source currents.

Step-by-Step Solution:

Verification / Alternative check:
Review the NE555 datasheet curves showing VOH vs. load current and VOL vs. sink current; the numbers cluster around these values at common loads.

Why Other Options Are Wrong:

• VOH = 10 V: implies rail-to-rail behavior not achievable by a bipolar 555 under load.
• VOL = 0 V: ignores saturation voltage.
• VOH = 8.5 V, VOL = 0 V: partly realistic but still assumes VOL = 0 V.

Common Pitfalls:
Confusing CMOS 555 (closer to rail-to-rail) with the bipolar version; ignoring load dependence.

Final Answer:
VOH = 8.5 V, VOL = 0.1 V