want to know the use of this type of diode connection???

[jaysenghani]

i've seen this circuit in many input and output side of opamp.
what this circuit does??
and please also tell working

 

[Tunelabguy]

This circuit is a 0.7 volt bipolar limiter. Because diodes only conduct when the forward voltage exceeds 0.7 volts, this circuit does nothing until the voltage exceeds that limit.

 

[jaysenghani]

This circuit is a 0.7 volt bipolar limiter. Because diodes only conduct when the forward voltage exceeds 0.7 volts, this circuit does nothing until the voltage exceeds that limit.

i just want to understand working of this circuit. if you have some circuit where this limiter circuit is used please share it and explain woking.

what happen if voltage is exceed 0.7v???

 

[barry]

It's for protection. Normally the voltage across the inputs to the opamp is close to zero.

 

[jaysenghani]

It's for protection. Normally the voltage across the inputs to the opamp is close to zero.

what type of protection???

 

[Tunelabguy]

Protection against over voltage.

 

[jaysenghani]

Protection against over voltage.

if i want to design this diode for 5V over voltage protection how to proceed for design??

 

[barry]

Connect the cathode to the input and then anode to +5Volts. Do that on both inputs.

 

[jaysenghani]

Connect the cathode to the input and then anode to +5Volts. Do that on both inputs.

not understand..

if you have schematic where this type of limiter is use please share and explain so i understand better

 

[barry]

Hope this attachment works...

 

[FvM]

As any protection circuit, the suggest diode clamp has a limited overload handling capability. The present circuit depends on current limited sources, otherwise it needs current limiting resistors. In addition, there's an undefined current sharing between external diodes and OP internal substrate diodes that possibly need to be solve by placing additional series resistors between diodes and OP input. Finally, a positive overload can possibly pull-up the supply voltage and invalidate the protection, unless supplemented by a power zener diode.

 

[picgak]

i've seen this circuit in many input and output side of opamp.
what this circuit does??
and please also tell working

this type of diode connection is used to limit the input of devices whose input is Ac and need to be protected from likely high varying Ac (this circuit limits the input to + or - 0.7v )

if i want to design this diode for 5V over voltage protection how to proceed for design??

for this you have to keep two 4.2v zener diodes connected in series anode to anode and inserted between the point tobe protected and ground