4 Channel NECL Terminator


$ 1,148.85


  • Replacement for discontinued HP/Agilent/Keysight 10086A ECL Terminator
  • Allow direct connection of NECL signals to 50 Ω input instruments
  • Provide standard 50 Ω/VTT terminations for NECL signals and Ground Referenced Outputs
  • Testing and monitoring GHz NECL signals in digital and wireless communication applications
  • Monitoring of optical transceiver outputs


  • 43 ps Typical Rise Time (8 GHz equivalent bandwidth)
  • 50 Ω/-2 V Input Termination for NECL
  • Ground Referenced Outputs protect sensitive instruments
  • SMA I/O connectors
  • 12 dB (4X) attenuation
  • Self-contained 1.3 x 2.9 x 2.2-in. unit includes AC/DC Adapter



NECL logic levels are offset from ground. Without proper level shifting, these logic signals can not be connected to ground-referenced 50 Ω input instruments, such as sampling 'scopes, network analyzers, scanners and counters, etc. Otherwise, either the NECL equipment outputs or the measurement instrument inputs may be made inoperative or damaged.

When driving a length of 50 Ω coaxial cable, a NECL output must be terminated into a 50 Ω load that is connected to a terminating voltage VTT = VCC -2 V. For NECL circuits operating with a supply voltage of either -5.2 V or -4.5 V, VCC is 0 V, and VTT is equal to -2 V.

NECL Terminators are level translators which convert NECL signals into signals that can be connected to ground referenced 50 Ω input instruments and, at the same time, provide standard 50 Ω/VTT terminations required by NECL signals.


The PRL-550NQ4X is a Four Channel NECL Terminator designed to interface with NECL circuits operating with a -5.2 V or -4.5 V supply. Each input has an equivalent 50 Ω resistor terminated to a voltage VTT = -2 V.

The outputs of these Terminators are designed for direct connection to ground-referenced 50 Ω input instruments as shown in Fig. 1, and a block diagram is shown in Fig. 2. These near-ground level output signals* protect sensitive instruments and enhance measurement accuracy when these instruments are used.

Once a NECL signal is translated through a proper Terminator, it can be routed through 50 Ω scanners and other high frequency measuring instruments for processing. Each PRL-550NQ4X Terminator is housed in an attractive 1.3 x 2.9 x 2.2-in. extruded aluminum enclosure and is supplied with a ±8.5 V AC/DC Adapter.

Fig. 1: NECL driving a 50 Ω input instrument using the PRL-550NQ4X Terminator
Fig. 2, PRL-550NQ4X Diagram

(0° C ≤ TA ≤ 35° C)*

Symbol Parameter PRL-550NQ4X Unit
Min Typ Max
RIN Input Resistance 49.5 50.0 50.5 Ω
VTT Input Termination Voltage -2.2 -2.0 -1.8 V
VOS Output Offset Voltage* -20 0 20 mV
  Signal Attenuation 11.8 12.0 12.2 dB
IDC1 DC Input Current, +8.5 V   +60 +85  
IDC2 DC Input Current, -8.5 V   -125 -150  
VDC DC Input Voltage ±7.5 ±8.5 ±12 V
VAC1 AC/DC Adapter Input Voltage, 120 V 103 115 127 V
tPLH Propagation Delay to output ↑   475 575 ps
tPHL Propagation Delay to output ↓   475 575  
tr/tf Rise/Fall Time   43 61 ps
BW Equivalent bandwidth  5.7 8.0   GHz
tSKEW Skew between outputs   20 50 ps
  Channel-to-Channel Cross Talk @ 1.4 GHz 34 40 dB
  Size 1.3 x 2.9 x 2.2 in.
  Weight, excluding AC adapter 5 Oz
  Shipping weight, including AC adapter 4 lb.
*The output offset and input termination voltages are factory set to 0 V and VTT = VCC-2 V, respectively, before the input is connected to an NECL device. When connected to an NECL device, the output low level will be slightly offset from ground depending on the low level output voltage of the connected device, which is typically VCC-1.8 V. When its input is connected to an NECL device, the Terminator output Low level is typically +50 mV.