Timer IC application — a 555 timer can be configured as an astable multivibrator (free-running oscillator) that produces a continuous square(ish) wave without an external trigger. Is this statement appropriate?

Introduction / Context:
The ubiquitous 555 timer IC is used in three classic modes: monostable (one-shot), astable (free-running), and bistable (flip-flop). In astable mode, the device continuously charges and discharges a timing capacitor between two threshold levels using external resistors, producing a periodic output. The question asks whether the 555 can indeed be configured as an astable multivibrator without external triggering.

Given Data / Assumptions:

• Standard bipolar or CMOS 555 device.
• External components RA, RB, and C are available for timing.
• Supply within device ratings; load does not excessively clamp the output.

Concept / Approach:
In astable mode, the 555 uses its internal comparators and SR latch to toggle when the capacitor voltage crosses 2/3 Vcc (threshold) and 1/3 Vcc (trigger). With RA and RB arranged so the capacitor charges through RA + RB and discharges through RB, the output oscillates continuously. The approximate formulas are: f ≈ 1 / (0.693 * (RA + 2RB) * C) and duty ≈ (RA + RB) / (RA + 2RB). A 50% duty cycle can be approached with additional diodes or alternative topologies but is not mandatory for oscillation.

Step-by-Step Solution:

Verification / Alternative check:
Prototyping on a breadboard with RA=10 kΩ, RB=10 kΩ, C=0.01 µF yields a frequency near 1/(0.693*(10k+20k)*0.01µF) ≈ 4.8 kHz, confirming astable operation.

Why Other Options Are Wrong:

Common Pitfalls:
Expecting an exact 50% duty without additional components; miswiring threshold/trigger nodes; using timing parts outside safe value ranges.

Final Answer:
Correct