Which multivibrator has one permanent stable mode of operation?

A monostable multivibrator is characterized by having one stable state and one unstable state. This means that in its normal condition, it will remain in the stable state until triggered by an external input. When the trigger pulse is received, the multivibrator briefly transitions to the unstable state, after which it returns to the stable state. This behavior is key in various timing applications, pulse generation, and signal conditioning where a single output pulse is needed in response to an input signal.

The permanent stable mode of operation refers to the fact that, unlike other multivibrators, a monostable multivibrator is predominantly inactive (or in a stable state) unless specifically triggered. In contrast, an astable multivibrator continuously oscillates between its two unstable states without any external triggering, while a bistable multivibrator has two stable states and can be flipped between them by inputs. A Schmitt trigger, while it provides a stable output for a given input, does not fit the classic categorization of multivibrator configurations as it is a comparator circuit with hysteresis rather than a traditional multivibrator configuration.