10

EL4331C

Triple 2:1 Mux-Amp AV = 1

A demonstration board with this circuit on it is available

from Elantec.

Application Circuit #2

Figure 2 shows a circuit that has either a very wide band-

width, or an 11 MHz low pass response. The EL4331’s

“A” inputs are connected to the one frequency determin-

ing set of components, while the “B” inputs are

connected directly. The A/B select pin therefore selects

the desired bandwidth. This would allow appropriate fil-

tering to clean up noisy low bandwidth video signals

when displaying them on a high quality wide bandwidth

monitor.

Application Circuit #3

Figure 3 shows one of the three channels of a component

video, 8:1 multiplexer. The A/B select pins naturally

allow binary coded addressing—allowing simple micro-

processor or state machine control. Note that each

amplifier output is loaded, to keep the amplifier outputs

damped.

Photograph A1 shows a staircase generated by having all

the inputs (sig0 through sig7) connected to a resistive

divider chain, and the select bits were driven by a binary

counter. Photograph A2 shows the glitch between steps

4 and 5; this is the worst glitch since all three banks of

EL4331s are switching together. The magnitude of this

glitch is affected by the timing skew of the select lines,

the physical length of the traces, and the difference in

amplitude of the two signals. This particular circuit was

bread-boarded using EL4331s on their adapter boards

(available from Elantec for those who can not bread-

board with SOICs), and the binary counter was an

'LS163.

Figure 2. A Bandwidth-Selectable Filter