Gm C filter transfer function urgent help please

Status
Not open for further replies.
Hi cleo,

here is the transfer function of your circuit: H(s)=N(s)/D(s)

N(s)=(+ H3 H1)

D(s)=(+ H4 H3) + ( - H2 C2) s + (C2 C1) s^2

The negative sign in the denumerator indicates that something is wrong since all expressions in D(s) must be positive.
A visual inspection of the circuit shows that you have positive dc feedback (see the second unit) thereby inhibiting linear operation.
Please check the circuitry.
 
Last edited:
Correction of the circuit: By changing the output polarity of the 2nd unit the minus sign will disappear.
Then, you will have a second order lowpass function.
 
LvW said:
Correction of the circuit: By changing the output polarity of the 2nd unit the minus sign will disappear.
Then, you will have a second order lowpass function.
Click to expand...


thanks verry much, it's very useful, i figured it out about how can i reach that result...and yes, u were right, that polarity is wrong....thanks again
 

The second unit with 100% feedback acts as a grounded resistor (R=1/g2=1/H2) in parallel with X=1/sC1
With this in mind you can apply the classical rules for OTAs with Vout/Vin=g*Xload.
The whole circuitry is the OTA representation of the classical opamp lowpass configuration consisting of a damped and an undamped integrating device connected in a closed loop.
 
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…