Datasheet

3-1
THS4226EVM Applications
THS4226EVM Applications
Example applications are presented in this chapter. These applications
demonstrate the most popular circuits to the user, but many other circuits can
be constructed. The user is encouraged to experiment with different circuits,
exploring new and creative design techniques. That is the function of an
evaluation board.
3.1 Inverting Video Gain Stage
The circuit described in Chapter 1 is an inverting gain stage with a voltage
divider on the output. Equation 1 indicates the gain when R2 is changed to
78.7 Ω, R5 is changed to 75 Ω and R4 is removed. Rt is the termination
resistance of the measurement device. The voltage gain from J2 to J1 is
simplified, as shown:
V
O
V
I
+*
R6
R1
ǒ
Rt
Rt ) R5
Ǔ
+ 0.5
(1)
R5 is used to match the output impedance of the amplifier to the line being
driven and the instrument taking measurements. For short transmission line
length, R5 can be replaced with a jumper.
R5 can also be used to isolate the amplifier from large capacitive loads.
Figure 3–1. Inverting Video Gain Stage
R5
R2
R6
J1
V2Out
J2
V2in––
Vs–
–
+
U1A
THS4226
2
3
1
10
4
R1
Vs+
R10
1.3 kΩ
75 Ω
49.9 Ω
78.7 Ω
1.3 kΩ
PD1
5
Chapter 3