Low Pass Active Filter
Typical Application Circuits
The low pass filter shown in Figure 6 has a DC gain of ( - R2 / R1 )
and the –3dB corner frequency is 1/2πR2C. Make sure the filter is
within the bandwidth of the amplifier. The Large values of feedback
resistors can couple with parasitic capacitance and cause undesired
effects such as ringing or oscillation in high-speed amplifiers. Keep
resistors value as low as possible and consistent with output loading
consideration.
Differential Amplifier
The circuit shown in Figure 4 performs the difference function. If
the resistors ratios are equal ( R4 / R3 = R2 / R1 ), then
V
OUT = ( Vp – Vn ) × R2 / R1 + Vref.
R2
C
R2
R1
Vn
R1
VIN
¼ SGM2324
VOUT
Vp
¼ SGM2324
VOUT
R3
R4
R3 = R1 // R2
Vref
Figure 4. Differential Amplifier
Figure 6. Low Pass Active Filter
Instrumentation Amplifier
The circuit in Figure 5 performs the same function as that in Figure 4
but with the high input impedance.
R2
R1
¼ SGM2324
Vn
¼ SGM2324
VOUT
Vp
R3
R4
¼ SGM2324
Vref
Figure 5. Instrumentation Amplifier
8
SGM2324
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
