Typical Application Circuits
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 ) × R
2
/ R
1
+ Vref.
C
R2
R1
V
IN
SGM8621
R2
Vn
Vp
R3
R4
Vref
Figure 4. Differential Amplifier
V
OUT
R1
SGM8621
V
OUT
R3=R1//R2
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
SGM8621
Vn
SGM8621
V
OUT
Vp
SGM8621
R3
R4
Vref
Figure 5. Instrumentation Amplifier
Low Pass Active Filter
The low pass filter shown in Figure 6 has a DC gain of (-R
2
/R
1
)
and the –3dB corner frequency is 1/2πR
2
C. 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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SGM8621/2/3 /4
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
