Signal amplification circuit

[ywcheung]

It is a bandpass filter

How to calucate the the Q value, fc, gain of this circuit.......

Anyone can explain or describe this circuit...thank you!!

How to improve this circuit to high Q

 

[teteamigo]

Put the equations of this circuit in s domain applying the Laplace Transform.

Then we have a algebraic relationship between input and output.

Two capacitors give at less a 2nd order system.

Then Q=damping factor of poles/natural no damped ressonance frequency =α/ω0

https://en.wikipedia.org/wiki/Q-factor

 

[ywcheung]

Put the equations of this circuit in s domain applying the Laplace Transform.

Then we have a algebraic relationship between input and output.

Two capacitors give at less a 2nd order system.

Then Q=damping factor of poles/natural no damped ressonance frequency =α/ω0

https://en.wikipedia.org/wiki/Q-factor

what is the equations of this circuit?? can you expain it in detail please?

and what you mean Two capacitors give at less a 2nd order system?

 

[shaikhsarfraz]

Hi,
He means to say that if you use a circuit with 2 capacitors than it will contribute 2 poles in the system.

Only thing is get the laplace transform of the system transfer function.

Than you can find the Q of the circuit from it.

thanks
sarfraz

 

[Kral]

ywcheung,
The circuit as drawn will not work. There is no DC path from the + input to ground. I'm assuming that you intendted to put a resistor in parallel with the capacitor (call it C2) from the + input to ground. Under this assumption, C2 has no effect on the transfer function. Without the added resistor, the input bias current from the op-amp will eventually charge C2 to the a voltage that will cause the op-amp to saturate.
.
With the modified circuit, let Ci be the input capcaitor, Ri the input resistor, Rf the feedback resistor. Then the transfer function is:
.
sRfCi/(1+sRiCi)
.
The circuit has one pole and one zero.
.
substituting jw for s will give you the frequency response
.
At DC, the gain is zero.
At w = infinity, the gain is approximately Rf/Ri.
.
The lag corner frequency is 1/RiCi radians per second.
Regards,
Kral.