74LS221 Dual Mono Multivibrator Schmitt Trigger


The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. The 74LS221 device is a dual multivibrator with performance characteristics virtually identical to those of the ’121 devices. Each multivibrator features a negative-transition-triggered input and a positive-transition-triggered input, either of which can be used as an inhibit input.

74LS221 Features

  • Dual, Highly Stable One-Shot
  • Pinout Identical to 74LS123
  • Hysteresis Inputs
  • Direct Reset Terminated Output Pulse
  • Standard TTL Switching Voltages

74LS221 Specifications

Supply Voltage4.75 – 5.25Vdc
Maximum Clock Frequency40Mhz
Power Dissipation2mW/gate @100kHz
Minimum Output Current8mA
Propagation Delay10nS
Fan Out (TTL Loads)20

74LS221 Pinout Diagram

74LS221 Pin Description

Pin NoPin NameDescription
11AInput 1 Of Schmitt Trigger 1
21BInput 2 Of Schmitt Trigger 1
31 CLR Clear Pin 1
41QOutput Of Schmitt Trigger 1
52QOutput Of Schmitt Trigger 2
62 C(ext)External Capacitor 2
72 R(ext)/C(ext)External Capacitor/Resistor 2
92AInput 1 Of Schmitt Trigger 2
102BInput 2 Of Schmitt Trigger 2
112 CLRClear Pin 2
122Q’Invert Output Of Schmitt Trigger 2
131Q’Invert Output Of Schmitt Trigger 1
141 C(ext)External Capacitor 1
151 R(ext)/C(ext)External Capacitor/Resistor 1
16VCCPositive Supply


  • Increase the noise immunity in a circuit with only a single input threshold

74LS221 Alternative Equivalent

Download 74LS221 Dual Mono. Multivibrator Schmitt Trigger Datasheet from the link given below.