The document discusses a seminar on Schmitt triggers. It begins with an introduction defining a Schmitt trigger as a bistable multivibrator circuit that remains in one state until the input passes a threshold level. It then describes the working of the circuit, including how it uses positive feedback and transistors as comparators to determine high and low thresholds. Finally, it lists important uses of Schmitt triggers such as converting input waveshapes to square waves and detecting when the input crosses trigger levels.

1. SEMINAR ON:

2. CONTENT
 Introduction
 Working of circuit
 Circuit diagram
 Output waveforms
 Applications
 Important uses of schmitt
trigger

3. INTRODUCTION
Schmitt is an important bistable multivibrator. It is
called schmitt trigger after the name of its
inventor.Using transistor it is basically an emitter-
coupled binary oscillator.The schmitt trigger circuit
is a threshold circuit with positive feedback having
a loop gain greater than one(1).The circuit is
named trigger because it remains in its value untill
the input changes sufficiently to trigger a change.
In the non inverting configuration when the input is
high than a certain choosen thershold, output is low
when the input is in between the two, the output
retain its value.

4. WORKING OF CIRCUIT
The original schmitt trigger is based on the
dynamic thershold idea i.e implemented by a
voltage divider with a switchable upper lag(RC1
and RC2) and steady lower lag (RE).
The T1 act as comparator ( A comparator is a
device that compares two voltage or current and
switches its output to indicate which one is
greater)with a differential input.(T1 emitter base
junction)The base of T1 is like a inverting and the
emitter and the emitter of the T1 and like a non
inverting input.This two determines the
thershold.The high and low thershold is
proportional to the value of RE (i.e the potential
difference across RE)

5. •Now ,When T2 is on conducting operation,Let us input
a trigger of the base of T1. Since T2 is conducting,the
high thershold is determined by the resistor RE (VIN must
be postive w.r.t VRE to get forward biased )When the VIN
is slightly above the value of VRE ,T1 begins conducting
and T2 being going cut-off,beacause now the T2 get less
current in its base.In this way the T2 is cut-off and we
get a higher output.
•Now let us lower the VIN , the thershold now also
depends upon the value of VRE because T1 will only cut-
off in the condition when VIN is less than VRE.So with a
little lower in the value of VIN, there is no change in the
output, but when the VIN lowers the values of VRE the T1
is cut off and T2 begins to conduct because now the
base of T2 gets higher current.Thus we get a lower
output in the output terminals.
In this way the schmitt trigger circuit works.

6. CIRCUIT DIAGRAM

7. OUTPUT WAVEFORMS

8. IMPORTANT USES OFF
SCHMITT TRIGGER ARE GIVEN
BELOW:
1.As a squaring circuit because it can convert
inputs of any waveshape into output pulses of
rectangular or square waveshapes.
2.As an amplitude comparator or level detector
because in schmitt trigger circuit a change of
state occurs whenever the input crosses a
trigger.
3.As a flip-flop circuit.
4.For reshaping the worn-out pulses by giving
them sharp leading and trailing edges.