Non-Inverting Schmitt Trigger using Operational Amplifier (Op-Amp) in English
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Non-Inverting Schmitt Trigger circuit using
Non-Inverting Schmitt Trigger circuit using Operational Amplifier (Op-Amp) in English
Introduction
Comparator circuit with positive feedback are called as Schmitt trigger
They have two stable states(+Vsat and –Vsat) (Bi-stable circuit)
It is a square wave generator
Hysteresis is found in Schmitt trigger circuit
Definition
The output voltage changes its states when ever input voltage exceeds certain voltage level ,upper threshold voltage VUT and lower threshold voltage VLT
Types of Schmitt Trigger
1.Inverting Schmitt Trigger
2.Non inverting Schmitt Trigger
Non inverting Schmitt Trigger
The input is applied at non inverting terminal of opamp and inverting terminal is grounded
Upper threshold voltage VUT
The value of Vin which makes the Vf=0 and forces the output to make the transition from
-Vsat to +Vsat
For V0 to switch from -Vsat to +Vsat
Vin crosses VUT
Vf crosses 0V (Vf greater than 0)
At the time of state change
Vin = VUT
Vf = 0V
Lower threshold voltage VLT
The value of Vin which makes the Vf=0 and forces the output to make the transition from
+Vsat to –Vsat
For V0 to switch from +Vsat to -Vsat
Vin crosses VLT
Vf crosses 0V (Vf smaller than 0)
At the time of state change
Vin = VLT
Vf = 0V
WORKING
The voltage present at the inverting terminal is compared with the voltage present at the non-inverting terminal
If Vf greater than 0
Vout = +Vsat
If Vf smaller than 0
Vout = -Vsat
Hysteresis
Hysteresis occurs when positive feedback is used in comparator
Due to hysteresis the comparator output makes transition at different points when comparator changes its state from low to high and high to low
Effect of Hysteresis
Noise immunity is improved
Response time reduces
Sensitivity of circuit is reduces as the circuit does not respond to input voltage changes in dead zone or in hysteresis range
False triggering due to noise is reduced
Advantages of Schmitt trigger
Due to positive feedback, the speed of response is increased
Due to hysteresis the problem of relay chattering is reduced as the Schmitt trigger does not change its output in hysteresis range
By adjusting the VUT and VLT the duty cycle of square wave can be adjusted
The monolithic Schmitt triggers are uncompensated, therefore they have high speed of response
Dis-advantage of Schmitt trigger
Sensitivity of Schmitt trigger decreases with increase in hysteresis because the circuit does not respond in hysteresis range
To overcome this problem
If value of Vin increases then VUT is reference voltage i.e. the output will not change at VLT
If value of Vin decreases then VLT is reference voltage i.e. the output will not change at VUT
Introduction
Comparator circuit with positive feedback are called as Schmitt trigger
They have two stable states(+Vsat and –Vsat) (Bi-stable circuit)
It is a square wave generator
Hysteresis is found in Schmitt trigger circuit
Definition
The output voltage changes its states when ever input voltage exceeds certain voltage level ,upper threshold voltage VUT and lower threshold voltage VLT
Types of Schmitt Trigger
1.Inverting Schmitt Trigger
2.Non inverting Schmitt Trigger
Non inverting Schmitt Trigger
The input is applied at non inverting terminal of opamp and inverting terminal is grounded
Upper threshold voltage VUT
The value of Vin which makes the Vf=0 and forces the output to make the transition from
-Vsat to +Vsat
For V0 to switch from -Vsat to +Vsat
Vin crosses VUT
Vf crosses 0V (Vf greater than 0)
At the time of state change
Vin = VUT
Vf = 0V
Lower threshold voltage VLT
The value of Vin which makes the Vf=0 and forces the output to make the transition from
+Vsat to –Vsat
For V0 to switch from +Vsat to -Vsat
Vin crosses VLT
Vf crosses 0V (Vf smaller than 0)
At the time of state change
Vin = VLT
Vf = 0V
WORKING
The voltage present at the inverting terminal is compared with the voltage present at the non-inverting terminal
If Vf greater than 0
Vout = +Vsat
If Vf smaller than 0
Vout = -Vsat
Hysteresis
Hysteresis occurs when positive feedback is used in comparator
Due to hysteresis the comparator output makes transition at different points when comparator changes its state from low to high and high to low
Effect of Hysteresis
Noise immunity is improved
Response time reduces
Sensitivity of circuit is reduces as the circuit does not respond to input voltage changes in dead zone or in hysteresis range
False triggering due to noise is reduced
Advantages of Schmitt trigger
Due to positive feedback, the speed of response is increased
Due to hysteresis the problem of relay chattering is reduced as the Schmitt trigger does not change its output in hysteresis range
By adjusting the VUT and VLT the duty cycle of square wave can be adjusted
The monolithic Schmitt triggers are uncompensated, therefore they have high speed of response
Dis-advantage of Schmitt trigger
Sensitivity of Schmitt trigger decreases with increase in hysteresis because the circuit does not respond in hysteresis range
To overcome this problem
If value of Vin increases then VUT is reference voltage i.e. the output will not change at VLT
If value of Vin decreases then VLT is reference voltage i.e. the output will not change at VUT
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