Skip to main content
Knowledgebase
Home
Renesas Electronics Europe - Knowledgebase

What is Transient response?

Latest Updated:11/01/2005

Question:

What is Transient response?

Answer:

Generally, a progress since a change has been given to a control system from an external source until the result reaches a steady state is called a transient response. In an electric circuit, this means time from when the input has changed to when a change in the output reaches a steady state.
For example, the switching time of a bipolar transistor and the reverse recovery time of a diode are examples of transient response.
The switching time of a transistor is specified by "turn-on time (ton) " and "turn-off time (toff) ", each of which is measured at points of 10% and 90% of the maximum amplitude of the input and output voltages/currents. In addition, the following parameters also determine the switching time of a transistor.

Delay timetd : Delay time since the pulse input has reached a level of 10% until the output current increases to a level of 10% (the voltage drops to 90%)

Rise timetr : Time until the output current increases from 10% to 90% (the voltage drops from 90% to 10%)

Storage timetstg : Time since the pulse input has reached 90% until the output current decreases to 90% (the voltage increases to 10%)

Fall timetf : Time until the output current decreases from 90% to 10% (the voltage increases from 10% to 90%)


These parameters are defined by a current. However, input/output waveforms are conventionally expressed in voltage. Therefore, the concept of output is reversed (the voltage drops when the current increases) .



These parameters define the switching time as follows (note that tr and tf define the current) .
Turn-on time ton=td+tr
Turn-off time toff=tstg+tf



The reverse recovery time of a diode is defined as time trr since the input voltage reverses from forward bias VF to reverse bias VR until it recovers to 10% of the maximum amplitude of the reverse current.

Suitable Products