All Datasheet Catalog of Datasheets, Circuit Schematics, Pinouts, & Projects

  • Increase font size
  • Default font size
  • Decrease font size
NE555 Datasheet, Circuit Schematic, Pinouts and Sources

NE555 Datasheet and Circuit Schematic Overview

The 8-pin 555 timer must be one of the most useful ICs ever made and it is used in many projects. With just a few external components it can be used to build many circuits, not all of them involve timing. A popular version is the NE555 and this is suitable in most cases where a '555 timer' is specified.

NE555 datasheet for download NE555N

NE555 Price Check

555 Timer IC Working Principal

Comparator 1 has a threshold input (pin 6) and a control input (pin 5). In most applications, the control input is not used, so that the control voltage equals +2/3 VCC. Output of this comparator is applied to set (S) input of the flip-flop. Whenever the threshold voltage exceeds the control voltage, comparator 1 will set the flip-flop and its output is high. A high output from the flip-flop saturates the discharge transistor and discharge the capacitor connected externally to pin 7. The complementary signal out of the flip-flop goes to pin 3, the output. The output available at pin 3 is low. These conditions will prevail until comparator 2 triggers the flip-flop. Even if the voltage at the threshold input falls below 2/3 VCC, that is comparator 1 cannot cause the flip-flop to change again. It means that the comparator 1 can only force the flip-flop’s output high.

To change the output of flip-flop to low, the voltage at the trigger input must fall below + 1/3 Vcc. When this occurs, comparator 2 triggers the flip-flop, forcing its output low. The low output from the flip-flop turns the discharge transistor off and forces the power amplifier to output a high. These conditions will continue independent of the voltage on the trigger input. Comparator 2 can only cause the flip-flop to output low.

From the above discussion it is concluded that for the having low output from the timer 555, the voltage on the threshold input must exceed the control voltage or + 2/3 VCC. They also turn the discharge transistor on. To force the output from the timer high, the voltage on the trigger input must drop below +1/3 VCC. This also turns the discharge transistor off.

A voltage may be applied to the control input to change the levels at which the switching occurs. When not in use, a 0.01 nano Farad capacitor should be connected between pin 5 and ground to prevent noise coupled onto this pin from causing false triggering.

Connecting the reset (pin 4) to a logic low will place a high on the output of flip-flop. The discharge transistor will go on and the power amplifier will output a low. This condition will continue until reset is taken high. This allows synchronization or resetting of the circuit’s operation. When not in use, reset should be tied to +VCC.



About the NE555 Timer

The 8-pin 555 timer must be one of the most useful ICs ever made and it is used in many projects. With just a few external components it can be used to build many circuits, not all of them involve timing! A popular version is the NE555 and this is suitable in most cases where a '555 timer' is specified. The 556 is a dual version of the 555 housed in a 14-pin package, the two timers (A and B) share the same power supply pins. The circuit diagrams on this page show a 555, but they could all be adapted to use one half of a 556.

Low power versions of the 555 are made, such as the ICM7555, but these should only be used when specified (to increase battery life) because their maximum output current of about 20mA (with a 9V supply) is too low for many standard 555 circuits. The ICM7555 has the same pin arrangement as a standard 555.

The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right. Usually just the pin numbers are used and they are not labelled with their function.

The 555 and 556 can be used with a supply voltage (Vs) in the range 4.5 to 15V (18V absolute maximum). Standard 555 timer and 556 ICs create a significant 'glitch' on the supply when their output changes state. This is rarely a problem in simple circuits with no other ICs, but in more complex circuits a smoothing capacitor (eg 100µF) should be connected across the +Vs and 0V supply near the 555 or 556.

The 555 has three operating modes:

  1. Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) etc.
  2. Astable - free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.
  3. Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.

NE555 Pinout

NE555 Pinouts


NE555 Circuit Schematic

ne555 Circuit Schematic


555 Timer IC Photo

Signetics NE555 photo


555 Timer Models and Manufacturers

Manufacturers Models/Types
National Semiconductors LM1455/LM555/LM555C
Motorolla MC1455/MC1555
Texas Instruments SN52555/SN72555, TLC555
RCA CA555/CA555C
Fairchild Semiconductors NE555/KA555
Philips (ECG) ECG955M
Exar XR-555
Maxim ICM7555
Sylvania NTE955M
STMicroelectronics NE555N/ K3T647
Zetex ZSCT1555
Raytheon RM555/RC555
Haris HA555
Intersil SE555/NE555/ICM7555

Project: Ignition Coil Driver with 2N3055 and 555 Timer

Here is a very simple circuit that will provide high voltage (15-40kV) sparks using a common ignition coil. The input is 12VDC at around 5 to 6 amps. Mine produces sparks that are about 3/4" to 1" in length. A 2N3055 NPN power transistor is pulsed with a square wave signal that comes from the 555 timer IC. The frequency of the pulses depends on the resistors between pins 7 and 8 and between pins 7 and 6. The pulse is also dependent on the capacitor. You can experiment with these values. Try inserting a smaller capacitor to raise the frequency. At different frequencies the sparks will change certain characteristics. At a high frequency the sparks will get fatter but shorter in length. At lower frequencies the spark maybe longer but thinner. I assembled my project on a solderless breadboard. You can use whatever you like. The capacitor should be a tantalum or mylar type, but this is not absolutely necessary. A ceramic type should work fine just as long as the temperature is not too high around it. Read more:

555 Timer IC, 2n3055 Ignition Coil Driver


Project: Using the NE555 in a Magnetically Operated Gun

The circuit is designed to produce a gun using the technology of magnet to drive a minimal hit a long distance horizontally or a few distance vertically. A magnet is an element that creates magnetic field which is a force that pulls on ferromagnetic materials and attracts or repel other magnets. It is created by moving charges such as electric current. It can also be created by the spin magnetic dipole moment, and by the orbital magnetic dipole moment of an electron within an atom.

NE555 IC Timer in Schematic of Magnetically Operated Gun

Circuit Explanation

The operation of the circuit starts with the 555 timer acting as oscillator being operated in astable mode where it performs pulse generation at a rate of 10 ms to the IC2 (4017B). The pin 15 will continue to take low at the fire button, while 4017B keeps on resetting. The outputs of Q1 to Q7 are sequenced by IC2 to provide power to TR1 to TR4 transistors. This in turn will launch in rapid sequence the inductors L1 to L4. The transformer can produce a 25.5 V DC to the electromagnets when rectified and leveled. The winding of the electromagnets on the copper tube will be cut in two after 500 turns. To slide one on the copper tube, the winding should be at the base of reversed sellotape. The physical size of the galvanized wire bullet is 2 mm diameter and 3 cm long. It should freely glide inside the copper tube.

Caution should be observed in positioning the electromagnets L1 to L4 on the copper tube to obtain optimum effectiveness on the movement of the bullet and arranging the voltage across resistor R1.

There are two basic types of electromagnetic gun, the rail gun and the coil gun. Both used stored energy to produce large magnetic field and high electric current through a driving armature. The interaction of the current with the magnetic field generates a force which propels the armature and any projectile connected to it.


555 Timer IC History: An Interview with Inventor Hans Camenzind

This Oral History is excerpted from an interview conducted in June, 2004.

In addition, reference is made to an article by Hans Camenzind, “Redesigning the old 555”, IEEE Spectrum, Sept 1997.

Hans, let’s start the Oral History with your recollections of the initial success of the 555 integrated circuit.

That 555 family was a total surprise.  I wanted to make it flexible, that was the whole purpose, but I didn’t realize it was so flexible.  There are applications now that still sound crazy to me.  And the quantity!  In the second year it moved to the largest quantity sold of any IC and it has stayed that way for 30 years.  The original application was as a timer and oscillator, but it has moved well beyond that.

According to the IEEE Spectrum article you wrote on the 555, there was reluctance at Signetics to invest in this product.  Is that right?

The engineering department at Signetics  - yes, they were a bit stodgy for a semiconductor company.  They were at the forefront.  They had tried everything.  It was a surprising reaction, and it was simply a reflection of the turf.  You know, they were designing and making operational amplifiers.
Was that their primary business?  

Yes, the primary linear business, although I think the digital portion (RTL and DTL) was still much larger. For the linear, op amp was king.  So they figured that if I designed a circuit that replaced one or two op amps, that would cut into their sales.

How did the 555 name come about?

Signetics had “500” numbers, and the earlier product I worked on was the 565, 566 and 567.  It was just arbitrarily chosen. It was Art Fury (Marketing Manager) who thought the circuit was gonna sell big who picked the name “555”.

I wonder how many of these have been made?

At the moment, it is about 1 billion devices a year.  These are mostly made in Korea now, Samsung.  The electronics industry is big now.

Are there other chips with this kind of popularity?

You could say that the op amp is bigger, but there are so many different op amps, they have to specialize – there is no perfect op amp, so you optimize it, for different parameters.  There must be 500 different op amp types.


555 Timer IC Datasheets and Related Keywords

ne555 Datasheet ne555 Data Sheet ne555 Application Note ne555 Equivalent ne555 Replacement
ne555 Fiche technique ne555 Scheda ne555 Ficha técnica de ne555 équivalent ne555 gleichwertige
ne555 Schematische ne555 Schéma ne555 Schematische ne555 Schematico ne555 Esquema
ne555 Component ne555 Reference Design ne555 Schematic ne555 Distributor ne555 Specs
ne555 equivalente ne555 Ersatz ne555 remplacement ne555 Mechanical Outline ne555 Features
ne555 Example ne555 RoHS ne555 Design ne555 Circuit ne555 Technical Specs
ne555 Errata ne555 User Guide ne555 Archive ne555 Datenblatt ne555 Ficha técnica
ne555 Prototype ne555 Design Idea ne555 Samples ne555 Inventory ne555 Stock
ne555 Revision ne555 Product Brief ne555 Release Notes ne555 Cross Reference ne555 MOQ
ne555 Lead Time ne555 Leadtime ne555 Xref ne555 Prototyping ne555 PDF
ne555 Capacity ne555 Availability ne555 Broker ne555 Distribution ne555 Catalog
ne555 EOL ne555 End-of-Life ne555 PCN ne555 Process Change Notification ne555 Explanation
ne555 Description ne555 Feature ne555 Operating Parameter ne555 Suffix ne555 Options
ne555 Pin-out ne555 Marking Code ne555 Electrical Characteristics