Output stage comparison: Do TTL totem-pole output stages typically switch faster than open-collector outputs that rely on external pull-up resistors?

Introduction / Context:
TTL outputs appear in two common forms: totem-pole and open-collector. Designers must know which style offers better transition times for high-speed logic and which is suited for bus sharing or level translation.

Given Data / Assumptions:

• Totem-pole outputs include an active pull-up transistor.
• Open-collector outputs require an external resistor to VCC for the HIGH level.
• Standard 5 V TTL logic families.

Concept / Approach:
Rise time at an open-collector output is set by the RC time constant of the pull-up resistor and total load capacitance (board traces, inputs). In contrast, a totem-pole actively sources current to charge capacitance rapidly, and actively sinks to discharge, producing faster edges and lower propagation delay.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets show significantly shorter rise times for totem-pole outputs than for the same device configured as open-collector with typical pull-ups.

Why Other Options Are Wrong:

• “Open-collector always faster” contradicts RC limitations.
• Voltage threshold (12 V) is irrelevant to TTL.
• Wire-ORing applies to open-collector buses, not to speed advantages.

Common Pitfalls:
Choosing too-weak pull-ups on open-collector lines, leading to slow edges and potential signal integrity problems at higher speeds.

Final Answer:
Yes — totem-pole outputs switch faster than open-collector outputs.