Thursday, June 8, 2017

555 Timer Circuit using LM324 and 7404 IC

Electronic Kit School. - Maybe you are usually using the popular time IC like LM555 in this time. But, do you know the internal block diagram of this 555 timer IC look like? Yes, when you want to know more about the internal circuit diagram of 555 timer IC you should read this article. 

When you using Proteus software, you can re draw the internal circuit of 555 timer IC look like shown in Figure 1 below. The internal diagram of this IC need some component like IC Lm324, RS Latch 7404 IC and others component.

In this time, beside we will show you the circuit, here we also will show you component part and global description about this circuit.


  1. Resistors
  2. LM324 IC
  3. RS Latch
  4. 7404 IC
  5. Transistor

Circuit like in Figure 1 above show you about the internal circuit diagram of 555 timer IC using the main LM324 and 7404 IC. From Circuitstoday site describe that 555-Timer is one of the most popular and mostly used ICs. It best suits for timing/timekeeping related circuits. It consists of two operational amplifiers operated in an open loop or comparator mode, RS Latch with additional Reset input, a discharge transistor, an inverting buffer and an amplifier in the output stage. It has a voltage divider circuit with three 5K Ohm resistors in series. 556 is a dual timer IC. 

The Upper comparator-UC is a Non-Inverting comparator, compares the input signal with 2/3Vcc and Lower comparator-LC is an Inverting comparator, compares input with 1/3 Vcc. The output of UC is given as R input of RS Latch and output of LC is given as S input of RS Latch. The RS Latch has an external Reset input which provides the option to reset the output instantaneously. The inverted output of Latch turns ON/OFF the discharge transistor. Inverting Buffer in the output stage inverts the output of Latch and drives the load.


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