Typical Application Circuits
C
Differential Amplifier
R2
The circuit shown in Figure 4 performs the difference function.
If the resistors ratios are equal ( R4 / R3 = R2 / R1 ), then
R1
VIN
V
OUT = ( Vp – Vn ) × R2 / R1 + Vref.
R2
VOUT
SGM721
R1
Vn
VOUT
SGM721
R3=R1//R2
Vp
R3
Figure 6. Low Pass Active Filter
R4
Vref
Figure 4. Differential Amplifier
Instrumentation Amplifier
The circuit in Figure 5 performs the same function as that in
Figure 4 but with the high input impedance.
R2
R1
SGM721
Vn
SGM721
VOUT
Vp
R3
R4
SGM721
Vref
Figure 5. Instrumentation Amplifier
Low Pass Active Filter
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.
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SGM721/2/3/4
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
