Once this is done, the output amp can be zeroed by taking a resistor (R37 or R38 plus associated pots) from pin 16 to VCC or ground.

Before trying to optimize the output pulse shape, look at the input pulse on pin 21, monitor point M4. Make sure that this is not oscillating. If it is not a clean pulse, increase the capacitance on pin 21. This is also a good place to slow down the IC. It takes a fairly large cap, 30 pF to 200 pF. Any oscillation on pin 21 is unacceptable and trying to cure it with the output amp adjustments can lead you into serious trouble as described below. However, as noted, if you have no compensation on the output amp pin 21 may show an oscillation. If increasing the size of the cap on pin 21 does not stop oscillation put a large comp cap, 15pf on the output amp compensation and recheck pin 21 to get the right value for the cap at pin 21 (C14). You can then reduce the compensation on the output amp to a suitable value.

Be careful how you use caps to remove oscillations of the output amplifier. There are two poles here, and you can actually make things worse by putting too large a cap across the feedback resistor. The cap (C8) from pin 18 to 19 is actually there to remove the effects of the stray input capacitance from the board, and should not be used to compensate the amp. This is particularly true if you try to remove incoming oscillations on pin 21 on the output amp. We suggest starting with a 5 pF comp cap (C10) from pin 20 to ground, and then removing any overshoot with a small cap (about 1 pF) from pin 18 to pin 19. You can make small changes from there. Our test board ran best with 1 pF from pin 18 to 19, and 3.9 pF from pin 20 to ground. At higher rail voltages C10 might have to be increased slightly.

Once again, if you are running at 20 MHz or less, you can be a little more generous with the comp cap and you can use 6 or 7 pF on the comp pin.

The output amp will drive 50 Ohms and should always be run with a load resistor of 300 ohms or less to prevent oscillation with a capacitive load, (probe). i.e probing the output pin may induce oscillations if you do not have a resistive load. With a picoprobe, or active probe, which has low capacitance it is not necessary to load the output. If you are using a buffer output amp, this is not necessary.  You can of course always use an external transistor with its base from the auxiliary output, tying its collector to an unregulated source and the emitter to ground if you do not want to stress the regulator. However, we have found this to be unnecessary.

Caution!  If you have negative pulses or undershoots from restorers that exceed the negative drive capability of the output amp with the load you have, put a diode or Schottky from the output to the auxiliary output, pin 17, with the anode on the output and the cathode on the auxiliary output.)

General discussion of speeding up and slowing down the L-17D.

The L-17D has been run with no serious overshoots or undershoots with a rise time of 6.5 nS at the start of logging, and a rise time of 4.5 nS for pulses 8 dB above the start of logging.To keep the noise as low as possible, you may want to slow the amplifier down. It is actually only necessary to do this for small pulses to keep the noise low, and this can be achieved by using a larger compensation cap on the output amp. However, this can result in slew-rate limitations. To slow the amp down at all frequencies we recommend a large capacitor (200 pF or larger) be connected from pin 21 to ground. To slow it down at small amplitudes only, you can use a larger comp cap on A2, pin 33 to ground (C16). Do not attempt to slowdown A1 by using a large comp cap there! Do not attempt to put an RC slow-down filter between A2 and A3!