The 74LS121 is a monostable Multi-vibrator with Schmitt-trigger inputs that features dual negative-transition-triggered inputs and a single positive-transition-triggered input which can be used as an inhibit input. The 74LS121 IC has a wide range of working voltage, a wide range of working conditions, and directly interfaces with CMOS, NMOS, and TTL. The output of the IC always comes in TTL which makes it easy to work with other TTL devices and microcontrollers.
What is a Monostable Multivibrator?
A monostable multivibrator (MMV), often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network, connected externally to the 555 timers. In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from a quasi-stable state to a stable state, energy is stored by an externally connected capacitor to a reference level. The time taken in storage determines the pulse width.
74LS121 Key Features & Specifications
- Logic Family / Base Number: TTL121
- Multivibrator Type: Monostable
- Output Current: 16mA
- Supply Voltage Min: 4.75V
- Supply Voltage Max: 5.25V
- Logic Case Style: DIP
- No. of Pins: 14Pins
- Propagation Delay: 45ns
- Logic IC Family: TTL
- Logic IC Base Number: 74121
- Operating Temperature Min: 0°C
- Operating Temperature Max: 70°C
74LS121 Pinout
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | Q’ | Active low output pin |
| 2 | NC | Not used |
| 3 | A1′ | Active Low Multivibrator input 1 |
| 4 | A2′ | Active Low Multivibrator input 2 |
| 5 | B | Schmitt Trigger Input |
| 6 | Q | Active high output |
| 7 | GND | Ground pin |
| 8 | NC | Not used |
| 9 | Rint | Pin to connect Rint resistance |
| 10 | Cext | Pin to connect Cext capacitance |
| 11 | Rext/Cext | Pin to connect Rext/Cext resistance/capacitance |
| 12 | NC | Not Used |
| 13 | NC | Not Used |
| 14 | Vcc | Chip Supply Voltage |
Applications
The 74LS121 IC has a number of uses , some of them are listed as below:
- monostable multivibrators are used as timers, delay circuits, gated circuits, etc.
74LS121 Datasheet
You can download the 74LS121 Monostable Multivibrator IC With Schmitt Trigger Inputs Datasheet from the link given below:
See Also: 74LS74 D-Type Positive Edge Triggered Flip-Flop | 74LS91 8-Bit Shift Storage Register | 74LS95 4-Bit Shift Register IC with Parallel I/O
