Dictionary of Electronic Terms
"A"
"B"
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z"
IC Monostable Multivibrator Timing
This first graph shows the possible output pulse width for either the 74121 or 74122 one-shot vs the timing resistor indicated [see the note below]. Find the External Resistor being used [Rx] move up the graph until the value of External Capacitor [Cx] is found and move left to find the value of the output pulse width.
74121/74122 Monostable Multivibrator Timing
Note 1; [embedded in graph] These values of resistance exceed the maximum recommended for use over the full temperature range. Both graphs indicate a supply voltage [Vcc] of 5 volts at a temperature of 25 degrees Centigrade.
This next graph shows the possible output pulse width for only the 74121 one-shot vs the external timing capacitor indicated [see the note below]. The graph below that works for using an external capacitor on a 74122. Find the External Capacitor being used [Cx] move up the graph until the value of External Resistor [Rx] is found and move left to find the value of the output pulse width.
74121 Monostable Multivibrator Timing
Note in graph; These values of resistance exceed the maximum recommended for use over the full temperature range.
Both graphs indicate a supply voltage [Vcc] of 5 volts at a temperature of 25 degrees Centigrade.
This graph below shows the possible output pulse width for only the 74122 one-shot vs the external timing capacitor indicated. Notice the increase in possible values for timing resistors.
74122 Monostable Multivibrator Timing
Precision components should be used in the circuit because these devices depend on the values of the resistors and capacitors attached to the IC. For example, using capacitors with a 10 percent will cause the timing to change by 10 percent each time the circuit is fabricated. The tolerance variation is on a per part basis, so one circuit implementation may appear to work when the capacitor value is close to the ideal value, while another fabrication of the circuit will show a different delay as the capacitor value differs because of component tolerance. Circuit layout and component placement also come into play because the components are effected by trace parasitics.
