bistable multivibrator

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The Bistable Multivibrator is another type of two state device similar to the Monostable Multivibrator we looked at in the previous tutorial but the difference this time is that BOTH states are stable.

1. Name:-dhaniraj r. yadav class:-t.y.b.s c . Div.:-’a’ roll no.: 29 seat no.: 13-16032 Topic name:- Bistable M ultivibrator Circuit’s I nformation Department :- Physics

2. BISTABLE MULTIVIBRATOR OTHER NAME THE COMPONENT VALUES HOW TO MADE CIRCUIT WHAT IS THE PRINCIPLE APPLICATION & SUMMARY REFERENCES

3. OTHER NAME BISTABLE MULTIVIBRATOR IS ALSO CALLED AS FLIP FLOP . AS THE NAME INDICATES,THE BISTABL E MULTIVIBRATO R HA S TW O STABL E STATES. THAT WHY CALLED BISTABLE MV.

4. HOW TO MADE CIRCUIT

5. CIRCUIT OPERATION B istable multivibrator, or a flip-flop, You will notice that it has two outputs and two inputs. The outputs are labeled Q and Q(NOT). The inputs are marked SET and RESET. The set and reset can be used to either preset the circuit or to use it as a memory storage device. If the trigger applied to the multivibrator causes the output (Q) to go high, the circuit is set. A set circuit is the equivalent of a closed toggle switch. If the trigger applied to the multivibrator causes the output (Q) to go low, the circuit is reset. When the circuit is in a reset condition, it is the equivalent of an open toggle switch.

6. Q1 on Circuits & Components. 2 Stable States; Q1 On, Q2 C/O Or Q2 On , Q1 C/O Frequency Out is ½ the Input. C 3 .001 f C 4 .001 f R 3 10 K  R 4 10 K  R 1 22 K  R 2 22 K  RC 1 1.5 K  RC 2 1.5 K  C 1 .001 f C 2 .001 f RB 1 & B 2 22 K  D 1 D 2 Q 2 Q 1 1 2 3 6 7 4 5 E O

7. When power is first applied to the circuit, both transistors begin to conduct. Due to component differences, one will conduct harder than the other. The harder conducting transistor drives the other transistor into cut-off. At that time, the conducting transistor goes into saturation. For this explanation, let's assume that Q1 is saturated and Q2 is cut off. depicts the current paths and voltage drops that provide the base bias for Q1 . As Q1 is in saturation, there will be around .7 volts DC across the emitter-base junction. Q2, being cut off, has no current flowing through it and has +Vcc on its collector. The voltage dropped across R5 and R3 places a positive voltage on the base of Q1 , keeping it ON. Even though Q2 is cut off, there will be a small voltage drop over R4 (< 1 volt DC) due to Q1's saturation.

8. Q1 off Q2 on Q1 on Q2 off. 4 Stable State; Q1 On , Q2 C/O Remains in stable state until triggered. D1 FB allows trigger to change conduction. C 3 .001 f C 4 .001 f R 3 10 K  R 4 10 K  R 1 22 K  R 2 22 K  RC 1 1.5 K  R C2 1.5 K  C 1 .001 f C 2 .001 f R B1 & B2 22 K  D 1 D 2 Q 2 Q 1 1 2 3 6 7 4 5 E O 1 2 a 2 2 b 2 a 3 3 a D 1 FB D 2 RB Frequency Out is ½ the Input.

9. Q1 in cut-off. As Q 2 is saturated, the voltage on its collector will be about 1 volt DC. The voltage divider formed by R3 and R5 places a potential of almost zero volts on Q1 's base. Q1, having ground on the emitter and almost zero volts OFF I on the base, will be reversed biased and cut off. This state is very stable. Unless an external action causes a change, Q2 will remain in saturation and Q1 will remain cut off. As this circuit is constructed from NPN transistors, a negative potential applied to the base of the saturated transistor (Q2) would cause it to go into cut-off. The action of cutting off Q2 would drive Q1 into saturation. The negative pulse would turn Q2, off placing +Vcc on its collector. R5 and R3 would divide the voltage, placing a positive voltage on the base of Q1 and turning it on. Now you are back where you started, with Q1 on and Q2 off.

10. Wave Form Q2 on Q1 off. 4 C 3 .001 f C 4 .001 f R 3 10 K  R 4 10 K  R 1 22 K  R 2 22 K  Rc 1 1.5 K  Rc 2 1.5 K  C 1 .001 f C 2 .001 f RB 1 & B 2 22 K  D 1 D 2 Q 2 Q 1 1 2 3 6 7 4 5 E O 3 3 b 1 2 a D 1 RB D 2 FB 2 2 b 3 a 2 a Frequency Out is ½ the Input. Stable State; Q2 On , Q1 C/O Remains in stable state until triggered. D2 FB allows trigger to change conduction.

11. SUMMARY Q 2 B Q 1 B Wave Form Analysis Frequency Out is ½ the Input. Stable State; Q2 On , Q1 C/O Remains in stable state until triggered . D2 FB allows trigger to change conduction. Stable State; Q1 On , Q2 C/O Remains in stable state until triggered. D1 FB allows trigger to change conduction. Read Signals: Left to Right Input @ 440 KHz Differentiated @ 440 KHz Rectified @ 220 KHz Output @ 220 KHz Q 1 Q 2

12. APPLICATION & SUMMARY The B istable M ultivibrator:. Has two stable states Requires an input trigger to change states Has two outputs, Q and Q’ The outputs are always opposite The output is taken from the collector of the transistors The major uses of a B istable M ultivibrator are :. Timing Frequency divider Memory storage device Electronic toggle switch

13. REFERENCES BY PROF.: Dr. M eena mam’s notes END THANK YOU