# Schematic Circuit Diagram of Internal block diagram of 555-Timer IC proteus simulation

555-Timer is one of the most popular and mostly used ICs. It best suits 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 internal block diagram of 555 is as follows;

Internal Block diagram of 555-Timer The Upper comparator-UC is a Non-Inverting comparator, that compares the input signal with 2/3Vcc and Lower comparator-LC is an Inverting comparator, that compares the input with 1/3 Vcc. The output of UC is given as the R input of RS Latch and the output of LC is given as the S input of RS Latch. The RS Latch has an external Reset input that provides the option to reset the output instantaneously. The inverted output of the Latch turns ON/OFF the discharge transistor. Inverting Buffer in the output stage inverts the output of Latch and drives the load.

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, divide voltages, bias active elements, and terminate transmission lines, among other uses. A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor.

The resistor absorbs the electrical energy in the process where it acts as a hindrance to the flow of electricity by reducing the voltage, and it is dissipated as heat. In today’s world of electronic circuits, heat dissipation is typically a fraction of a watt. The formula to calculate the resistance using Ohm’s Law is given as follows: R = V I. where R is the resistance of the resistor R in ohms (Ω) V is the voltage drop in the resistor in volts.

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