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.74LS161 synchronous, presettable counters feature an internal carry look-ahead for application in high-speed counting designs. The 161 is a 4-bit binary counter. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when structured by the count-enable inputs and internal gating.

74LS161 Features
- Edge Triggered High-Speed 4-bit Synchronous (Binary) Counters
- Asynchronous Master Reset
- Count Rate of 35MHz
- Operating Temperature up to 70°C
- Standard TTL Switching Voltages
74LS161 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 |
74LS161 Pinout Diagram

74LS161 Pin Description
Pin No | Pin Name | Description |
1 | CLR’ | Clear Pin |
2 | CLK | Clock Pin |
3 | A | Data Input Of Counter A |
4 | B | Data Input Of Counter B |
5 | C | Data Input Of Counter C |
6 | D | Data Input Of Counter D |
7 | ENP | Enable Pin |
8 | GND | Ground |
9 | LOAD’ | Load Pin |
10 | ENT | Enable Pin T |
11 | QD | Output Of Counter QD |
12 | QC | Output Of Counter QC |
13 | QB | Output Of Counter QB |
14 | QA | Output Of Counter QA |
15 | RCO | Ripple Carry Output |
16 | VCC | Positive Supply |
Applications
- Frequency counters
- Digital clocks
- Analog to digital converters
- With some changes in their design, counters can be used as frequency divider circuits
- In time measurement
74LS161 Alternative Equivalent
74LS163
Download 74LS161 Synch 4-bit Counter Datasheet from the link given below.