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.
VOUT
SGM8651
R2
R1
Vn
R3 = R1 // R2
VOUT
SGM8651
Vp
R3
Figure 6. Low Pass Active Filter
R4
Vref
Driving Video
The SGM865x can be used in video applications like in Figure 7.
Figure 4. Differential Amplifier
Instrumentation Amplifier
VIN
75Ω
SGM8651
The circuit in Figure 5 performs the same function as that in
Figure 4 but with the high input impedance.
75Ω
CABLE
RF
VOUT
R2
RG
R1
75Ω
SGM8651
Vn
SGM8651
VOUT
G = 1 + RF / RG
Figure 7. Typical Video Driving
Vp
R3
R4
SGM8651
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.
９
SGM8651/2/3/4/5
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
