The Model 620AL 8-Channel Discriminator is an extremely popular, low cost, 8-fold discriminator, combining the most useful operating features of general-purpose dis- criminators with the high packaging density, economy, and improved input characteristics afforded by a hybrid circuit input stage.
The 620AL offers a low minimum threshold of -30 mV, which is variable up to -1 volt via front-panel screwdriver adjustment and continuously variable up to -600 mV. A threshold monitor point is provided to permit the measurement of the threshold level with a common voltmeter rather than the more difficult and less precise analog measurement via oscillos- cope. The stability of the threshold is < 0.20%/'C to assure accurate results in varied operating environments. Because of the extremely low reflections from its input (20/o), the 620AL is significantly more protected against multiple pulsing due to reflections at -30 mV than the standard 10% reflection discriminators are at -50 mV.
The Model 620AL was designed to operate at maximum rates in excess of 1 00 MHz. It is a non-updating unit, requiring that its output returns to zero before it will again retrigger. At minimum output width setting, the 620AL will respond to a second pulse within 8 ns after the leading edge of the first pulse. Propagation delay through the 620AL is approximately 7.5 ns.
The outputs of the 620AL are low impedance voltage outputs, providing output levels greater than -800 mV into a 50 Ohm load. The output durations are independently presetta- ble via front-panel screwdriver adjustment from 5 ns to greater than 20 ns.Output rise and falltimes are less than 2.5 ns.
SPECIFICATIONS
NIM Model 620AL
8-CHANNEL DISCRIMINATOR
INPUT CHARACTERISTICS
Signal Input: Threshold, -30 mV to approximately -1.0 volt, (common to all channels, continu-
ously variable up to -600 mV); front-panel screwdriver adjust (screwdriver in-
cluded) 50 Ohm +/-1%, protected to +/- 5A for 0.5 As clamping at + 1 and -7 volts;
reflections <2% for input pulses of 2 ns risetime; stability <0.2%/'C to 600 C
operating range; offset 0 +/- 1 mV; threshold monitor 1 0: 1 ratio of monitor voltage
to actual voltage, +/-2%.
Gate: Slow gate via rear connector and rear panel ON-OFF switch; risetimes and
falltimes approximately 50 ns; clamp to ground from +5 inhibits; direct-coupled.
OUTPUT CHARACTERISTICS
3 NIM-level voltage outputs, quiescently 0 volts, -800 volts during output; dura-
tion : 5 ns to > 20 ns, continuously variable via front-panel screwdriver control
(narrower minimum width possible at slight expense of amplitude), risetimes
and falltimes typically 2.0 ns (max. 2.5 ns), 10% to 90%. Width stability better
than +/- 0.20%/' C maximum.
GENERAL
Maximum Rate: > 100 MHz, input and output.
Double-Pulse Resolution: Less than 10 ns.
Time Slewing: 1 ns. for input amplitudes 1 1 0% of threshold and above.
Input-Output Delay: 7.5 ns nominal.
Multiple-Pulsing: None; one and only one output pulse of preset duration is produced for each
input pulse, regardless of input pulse amplitude or duration.
Packaging: In RF shielded AEC/NIM #1 module; Lemo-type connectors.
Current Requirements: +6 V at 160 mA +12 V at 12 mA -24 V at 39 mA
-6 V at 400 mA -12 V at 172 mA