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. 74LS123 d-c triggered multivibrators feature output pulse-duration control by three methods. The basic pulse time is programmed by the selection of external resistance and capacitance values (see typical application data).

74LS123 Features
- Two Independent Retriggerable Monostable Multivibrators
- Retriggerable to 100% Duty Cycle
- Input Clamp Diodes
- Operating Temperature up to 70°C
- Standard TTL Switching Voltages
74LS123 Specifications
Supply Voltage | 4.75 – 5.25Vdc |
Maximum Clock Frequency | 40Mhz |
Power Dissipation | 2mW/gate @100kHz |
Minimum Output Current | 8mA |
Propagation Delay | 10nS |
Fan Out (TTL Loads) | 20 |
74LS123 Pinout Diagram

74LS123 Pin Description
Pin No | Pin Name | Description |
1 | 1A | Data Input Pin 1A |
2 | 1B | Data Input Pin 1B |
3 | CLR’ | Invert Clear Pin |
4 | 1Q’ | Active Low Output 1 |
5 | 2Q | Active High Output 2 |
6 | 2 C(ext) | External Capacitor 2 |
7 | 2Rext/C(ext) | External Resistor/External Capacitor 2 |
8 | GND | Ground |
9 | 2A | Data Input Pin 2A |
10 | 2B | Data Input Pin 2B |
11 | 2CLR’ | Invert Clear Pin 2 |
12 | 2Q’ | Active Low Output 2 |
13 | 1Q | Active High Output 1 |
14 | 1 C(ext) | External Capacitor 1 |
15 | 1 R(ext)/C(ext) | External Resistor/External Capacitor 1 |
16 | VCC | Positive Supply |
74LS123 Circuit
Applications
- Timers
- Pulse generators
- waveform generators
- Sweep generators for CRTs (cathode ray tubes)
74LS123 Alternative Equivalent
74LS423,74LS122
Download 74LS123 Dual Mono Multivibrator With Clear Datasheet from the link given below.