1. 1. A PRESENTATION ON 555 TIMER IC & its APPLICATION For the subject of ANALOG CIRCUIT DESIGN (code:2141002) DEPARTMENT OF ELECTRONICS ENGINEERING Presented by: Subham Dhar (130070110081) BIRLA VISHVAKARMA MAHAVIDYALAYA
2. 2. 555 TIMER & ITS APPLICATION Timer IC 555 is a monolithic timer IC The basic building blocks of 555 timer are:- a)RS Flip Flop, b)two comparators c)Reference Voltage Source d) Discharge transistor
3. 3. 555 CONFIGURED AS A MONOSTABLE CIRCUIT FF=flip-flip, depicted as a DPDT switch. Resistive divider comparator + is the pos. of the battery=9V - is the neg. term. of the battery=0V R R R +6 V +3 V (Assumption: pin #3 is connected to 0V)
4. 4. COMPARATOR comparator Each comparator compares two inputs and delivers an output depending on whether the inputs are similar or different. UP and DOWN remind you what each comparator does when it is activated. We will assume that the FF is in the up position when the 555 timer IC is powered up.
5. 5. 555 CONFIGURED AS A MONOSTABLE CIRCUIT Step 1: Ground pin 2, The output voltage of comparator A goes up Pin 7 will be disconnected from the ground. Step 2: C4 will get charged through R4. The voltage at pin 6 will go up. You dont need to memorize this. Just look at switch drawn in the FF. 0 V 0 V
6. 6. 555 CONFIGURED AS A MONOSTABLE CIRCUIT Step 3: The voltage at pin 6 will take some time to rise up to 9. Step 4: Note that the voltage at pin 5 is fixed to 2/3 of 9 V. When the voltage at pin 6 exceeds the voltage at pin 5, the output (pin 3) will be grounded and pin 7 will again be connected to ground. (You dont need to memorize this. Just look at the switch in the flipflop.) 0 V +6V
7. 7. SAMPLE WAVEFORM
8. 8. 555 CONFIGURED AS AN ASTABLE CIRCUIT
9. 9. OPERATIONS OF ASTABLE TIMER Lets assume that C1 is initially grounded. Step 1: A low voltage at pin 2 causes the Comparator to send a down signal to FF. Step 2: The output voltage at (pin 3) goes up and the pin 7 is disconnected from R2. (Again, look at the switch in the FF) Step 3: C1 gets charged up through R1+R2. Step 4: The voltage across C1 goes up. Step 5: The voltage at pin 6 exceeds the voltage at pin 5. Step 6: The comparator sends a high signal to the flip flop. Step 7: The voltage of Pin 7 goes to ground and The voltage goes to ground. Step 8: C1 discharges through R2. Step 9: Go back to step 1.
10. 10. FREQUENCY OF AN ASTABLE OSCILLATOR
11. 11. WHAT IF WE NEED A CLOCK?
12. 12. SQUARE WAVE OSCILLATOR USING 555 TIMER IC
13. 13. A CLOSER LOOK AT THE SQUARE WAVE GENERATOR
14. 14. PIN OUT DIAGRAM
15. 15. REFERENCE www.falstad.com www.microelectronics.com www.stelectronics.com IEEE signal processing magazine(2008) http://www.falstad.com/circuit/e-555int.html
16. 16. THANK YOU