Transcript
B.V.RAJU INSTITUTE OF TECHNOLOGY
Vishnupur , Narsapur , Medak (Dt)
(Affiliated to JNTU, Hyderabad)
2015
Technical Seminar
On
PRESENTED
BY
R.MANIKANTA
(14211D5707)
Definition Of CMRR?
CMRR=Adm/Acm
How to introduce noise in
CMRR
What is Gyrator??
o A 180 degrees phase shift occurs for signals traveling from
port-1 to port-2 and zero phase shift occurs for a signals
traveling from port-2 to port-1.
INTRODUCTION
As for differential signal transfer in these filter circuits,
it is important to consider normal/common-mode noise.
For the common-mode noise rejection, the filter circuits
generally applied a differential amplifier with a common-
mode feedback (CMFB) scheme
FCMFB scheme
Active inductor with gyrator-C network.
Floating active transformer.
Gm amplifiers consist of the CMFB scheme with common
resistances.
The CMFB scheme keeps the DC voltage of the output
constant
In this circuit, the DC levels of the input/output should be
lower/higher than half of the VDD
By adding Gm amplifiers, Gm3, to the ladder
structure, we can reduce common-mode noise.
It is shown in fig floating active transformer.
Each port of the differential signal is inverted and connected
to the opposite side
Half part of floating active transformer.
- I1 + V3Gm2 =0: node 1;
- I2 + V4Gm2 = 0: node 2;
sCV3 -V1Gm1 + V2Gm3 = 0: node 3;
sCV4 - V2Gm1 + V1Gm3 = 0: node 4;
V1 = sL11I1 + sM12I2 =
sCI1
+
sCI2
Gm2Gm3_ Gm1Gm2_
V2 = sL22I2 + sM21I1 =
sCI2
+
sCI1
Gm2Gm3_ Gm1Gm2_
L11 = L22 =
C
; M12 = M21 =
C
Gm2Gm3_Gm1Gm2
_
_ Del
=
Gm12 _-Gm3
2
/Gm1Gm3
When we set a larger equivalent mutual conductance, more
noise reduction can be achieved.
we can control the mutual inductance M and the inductance
Lby changes of the parameter Gmx. When Gm3 increases, M
increases
Circuit configuration of 6th order LC-ladder LPF with common-mode noise
reduction.
Using this active transformer, simultaneous LC-ladder filter
operation and common-mode noise reduction is possible.
Conclusion
References
THANK YOU
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