9

3550.6

February 8, 2006

Referring to Figure 10, both inputs are terminated in their

characteristic impedance; 75

Ω is typical for video

applications. Since the drivers usually are terminated in their

characteristic impedance the input gain is 0.5, thus the

frequency response of the amplifier so you should refer to the

both amplifiers from being active simultaneously. If this design

is extended to more channels the drive logic must be designed

loop of the amplifier so that the large open loop amplifier

output impedance while keeping the amplifier stable for all

values of load capacitance.

The circuit shown in Figure 10 was tested for the full range of

capacitor values with no oscillations being observed; thus,

problem one has been solved.The frequency and gain

characteristics of the circuit are now those of the amplifier

independent of any multiplexing action; thus, problem two

has been solved. The multiplexer transition time is

approximately 15

µs with the component values shown.

INPUT B

+

-

-5V

+

-

+5V

INHIBIT

CHANNEL

SWITCH

INPUT A

75

75

1N4148

100K

2000

0.047

µF

2000

1N4148

681

1

2

3

4

16

681

27

0.01

µF

681

27

681

0.01

µF

OUTPUT

7

6

5

13

10

0.047

µF

NOTES:

FIGURE 10. LOW IMPEDANCE MULTIPLEXER

100

Ω

(NOTE 17)

100

Ω

(NOTE 17)

HA5024