6.  SETTING UP THE L-17D

Since the IC has very high f_t transistors, it can rectify any high speed oscillations that may be present on the board or which originate from the RF section of a DLVA. These may be at several GHz and may be unobservable on your scope. If present, they will lead to DC shifts when you shift the position of the board, or move your hands over the board. We strongly recommend multilayer construction with a solid ground plane on the top layer. Also, isolate any long lines by running them between power or ground layers. In particular, use shielded cable for the input and output, and run the shielded cable as close to the IC as possible. If you are running at 20 MHz or slower this is not as important, but once you start to increase the bandwidth, it does become an issue.

The L-17D is sensitive to inductance in the power leads, so all power leads should be decoupled right at the power pins. This is actually only really crucial on VCC1, but it is best to solder decoupling caps directly from the power pins to ground if at all possible.

Ground the lid! If the lid is left floating, it can couple external high frequencies to the internal wire leads. If the IC has an identifying label on the lid that ends in a G, e.g. 08J03BG, it is not necessary to ground the lid externally as it has been connected in the package.

Whenever voltages are measured using a voltmeter, the measurement should be made with a 10KΩ resistor in series with the meter, i.e. place a 10K resistor on the point you are measuring and connect the wire from the meter to other end of the resistor, rather than connecting it directly to the desired point. This prevents pickup from the meter leads from affecting the reading.

The L-17D can be run at any rail voltages from ± 5V to ± 9V. Higher voltages will extend the dynamic range somewhat by increasing the maximum voltage outputs you can get from both the output amplifier and A1. If you use more than ± 7 volts, make sure that you have ample thermal contact to the board, or a heat sink to cool the chip. The chip can be run up to 125C.

You may or may not want to use a voltage regulator on board, depending on system issues. For test boards, an on-board regulator is not necessary, and the main decoupling capacitors need not be larger than 4 µF. If you are driving a 50-ohm line with the output, you may want to increase the capacitor size on VCC. We have not had to do this, but it may be necessary in some layouts.

When probing the monitor points with a scope probe, we strongly recommend you use a probe that has a very short ground attachment that is grounded on the ground plates surrounding the monitor point. Using the usual ground lead that is 10 cms long will give a distorted view of the pulses.