Typical Application Circuits
Differential Amplifier
C
The circuit shown in Figure 4 performs the difference function.
If the resistors ratios are equal ( R4 / R3 = R2 / R1 ), then
VOUT = ( Vp – Vn ) × R2 / R1 + Vref.
R2
R1
VIN
R2
VOUT
SGM8521
R1
Vn
VOUT
SGM8521
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
SGM8521
Vn
SGM8521
VOUT
Vp
R3
R4
SGM8521
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.
7
SGM8521/8522/8524