Driving Video
Typical Application Circuits
The SGM809x can be used in video applications like in Figure 5.
Differential Amplifier
The circuit shown in Figure 3 performs the difference
function. If the resistors ratios are equal ( R4 / R3 = R2 / R1 ),
then VOUT = ( Vp – Vn ) × R2 / R1 + Vref.
VIN
75Ω
SGM8091
75Ω
CABLE
R2
RF
VOUT
RG
R1
Vn
75Ω
VOUT
SGM8091
Vp
G = 1 + RF / RG
R3
Figure 5. Typical Video Driving
R4
Vref
Figure 3. Differential Amplifier
Low Pass Active Filter
The low pass filter shown in Figure 4 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.
C
R2
R1
VIN
VOUT
SGM8091
R3 = R1 // R2
Figure 4. Low Pass Active Filter
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SGM8091/2/3/4
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
