Microchip Technology dsPIC33CK - Page 59

Design Details
 2020 Microchip Technology Inc. DS50002927A-page 59
FIGURE C-3: FILTER, FEEDBACK AND BIAS CIRCUIT
Equation C-1 provides the amplifier gain calculations. Equation C-2 and Equation C-3
provide the equations to calculate cutoff frequencies of the Differential-mode and
Common-mode filters.
EQUATION C-1: AMPLIFIER GAIN
EQUATION C-2: CUTOFF FREQUENCY DIFFERENTIAL-MODE FILTER
EQUATION C-3: CUTOFF FREQUENCY COMMON-MODE FILTER
C2
RIN
RIN
C1
C2
R
F
RF
RIN
RIN
A
B
C
D
E
F
R
IN2
R
IN1
R
IN1
R
IN2
Differential Amplifier Gain =
Rf
(R
IN1
+ R
IN2
)
Differential-mode f
–3dB

1
2(R
IN1
+ R
IN2
)
C2
2
+ C1




Common-mode f
–3dB

1
2(R
IN1
)(C2)