Operating Procedures

1. Setting the operating point

An optimal DC bias must be provided to operate a video pack and acquire the stipulated output dynamic range and

bandwidth characteristics. Basically, the center point output voltage with no input should be set according to the

following formula.

While the optimal operating point when an AC input is applied will be similar, the recommended electrical

characteristics should be referred to when setting the operating point. The figures below show the DC and AC

waveforms when the Sanyo test jig is used. The design of this product series was optimized so that these products

provide adequate high-power characteristics.

2. Optimal peaking technique for mounted products (VP503 Series)

• Termination LC peaking

As can be seen from the internal equivalent circuit diagram, this series differs from earlier series in that peaking is

not applied using an internal coil. Since the high-frequency region peaking point is determined by an LC resonator

at the termination, the total distributed capacitance of the output side is particularly important. Accordingly, since

the independent evaluation board timing characteristics will differ from the actual output load capacitance when an

output cable is installed, the high-frequency area peaking point that corresponds to the output load state in the

mounted circuit must be found.

(Adjust the circuit using an output matching RC circuit at the same time.)

• RC emitter peaking

The purpose of the emitter peaking value is to increase the AC gain from the mid-frequency area to the high-

frequency area. This should be determined last, after adjusting the termination peaking and output peaking RC

circuits. (To compensate for high-frequency gain degradation at the IC side.)

• Output matching RC circuit

This circuit is used in conjunction with the peaking compensation in each section to match the IC internal

impedance with the output load impedance. Mount this RC circuit in the vicinity of the protection diode and the IC

output pins. Adjust this circuit to correct system characteristics while observing the mid-frequency characteristics,

the amount of overshoot in the pulse response, and other aspects. Since the AC gain from the mid-frequency area to

the high-frequency area will be reduced somewhat by this adjustment, determine the setting by adjusting the value

of the resistor precisely.

The required circuit operating conditions can be set up smoothly if the following flowchart is used to adjust the

peaking values.

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VP503