2 Channel Comparator, RS-422 Outputs


$ 1,397.25


  • Window Comparators
  • High Speed Timing
  • Line Receivers
  • Threshold Detection
  • Peak Detection
  • RS-422 Translation


  • fMAX > 500 MHz
  • 1.1ns Typical tr
  • +50 mV, 0 V or -50 mV Preset Input Threshold Voltage
  • -2.0 V to +3.0 V Input Common Mode Range
  • 10 mVPP Minimum Input @ 100 MHz.
  • DC Coupled 50 Ω Inputs
  • Differential 124 Ω Outputs
  • SMA inputs with SMA or Triax Output Connectors
  • Self-contained 1.3 x 2.9 x 3.9-in. unit includes AC/DC Adapter


The PRL-350RS is a ready-to-use, high-speed, dual-channel comparator module with RS-422 outputs. The PRL-350RS has a typical maximum clock frequency in excess of 500 MHz and has differential RS-422 outputs designed for driving floating 124 Ω transmission lines.

The PRL-350RS has DC-coupled 50 Ω inputs and differential 124 Ω outputs. The input threshold voltage can be selected either from a set of preset values of +50 mV, 0 V or -50 mV using a common three-position switch, or varied independently for each channel by applying a DC bias voltage to one of the two inputs. The input Common Mode Range is -2.0 V to +3.0 V.

The input threshold voltage can also be varied independently in each channel by applying an external DC bias voltage or shunt resistor to the D input.

  • If the external DC bias has a sufficiently low output impedance, it will over-ride the internally-generated VTH, and the toggle switch setting is a don’t-care.
  • For an external shunt resistor, the effective threshold voltage, VTHE, will be the result of the resistor-divider network formed by the external shunt resistor and the internal 50 Ohm termination to the selected VTH.
  • In the following example, the internal VTH is set to +50 mV, and it is pulled down to an effective VTHE of +10 mV via a 12.5 Ω shunt resistor:
  • This technique is typically provides a more useful operating range when using the PRL-350RS-NIM (special order), with settable ±400 mV thresholds.
  • To prevent oscillation, the external shunt resistor should be placed as close as possible to the D input, e.g. by using the male end of the PRL-PINET-SMF or similar device.

These high-speed comparators are Mini Modular Instruments™ that can be used as peak detectors, threshold detectors, sinewave-to-square wave converters, window comparators or differential line receivers, etc. The typical minimum input voltage of 10 mVPP is required for up to 100 MHz. It is recommended that the non-driven input be terminated into 50 Ω when the input frequency is near fMAX and its amplitude is less than 20 mVPP.

The PRL-350RS model has SMA input and output connectors. The PRL-350RSTR has SMA inputs and Triax output connectors. Each unit is supplied with a ±8.5 V AC/DC Adapter and housed in a 1.3 x 2.9 x 3.9-in. extruded aluminum enclosure

Fig. 1D PRL-350RS Block Diagram
PRL-350RSTRFig. 1E PRL-350RSTR Block Diagram

Anritsu Application Note for PON Module Testing with Anritsu MP1800A
Signal Quality Analyzer and PRL-350 Series Comparators (1.1 MB PDF)

BERT Level Translation

Anritsu engineers and customers around the world rely on our PRL-350 Series comparators for level conversion when testing Passive Optical Network (PON) modules.

PON module testing often requires converting the -1.0 to 0 V signals output by the MU181020A Pulse Pattern Generator cards to the LVTTL, PECL or LVPECL levels required by many ONU and OLT modules, typically for the Data, Pre-bias, and Reset signals.

Popular models include:

  • PRL-350TTL, Dual Channel Comparator with TTL Outputs
  • PRL-350LP, Dual Channel Comparator with LVPECL Outputs
  • PRL-350P, Dual Channel Comparator with PECL Outputs

App Note and block diagram copyright and courtesy of Anritsu Corporation.

(0° C ≤ TA ≤ 35° C)*

Unless otherwise specified, dynamic measurements are made with all outputs terminated into 50 Ω/VTT, where VTT = +3 V for PECL outputs.

Symbol Parameter PRL-350RS Unit
Min Typ Max
RIN Input Resistance 49.5 50 50.5 Ω
ROUT Output Resistance 123 124 125 Ω
VTH+ Preset positive threshold voltage 45 50 55 mV
VTH- Preset negative threshold voltage -55 -50 -45 mV
VTH0 Preset zero threshold voltage(1) -10 0 10 mV
VOLNL Output Low Level, No Load -1.2 -1.0 -0.8 V
VOLFL Output Low Level, 124 Ω Load -0.2 0 0.2 V
VOHNL Output High Level, No Load 2.75 3.0 3.3 V
VOHFL Output High Level, 124 Ω Load 1.8 2.0 2.2 V
IDC1 DC Input Current, +8.5 V 165 175 mA
IDC2 DC Input Current, -8.5 V -235 -250 mA
VDC DC Input Voltage ±7.5 ±8.5 ±12 V
VAC AC/DC Adapter Input Voltage 103 115 127 V
tPLH Propagation Delay to output↑ 2 ns
tPHL Propagation Delay to output↓ 2 ns
tr/tf Rise/Fall Times(2) 1100 1250 ps
tSKEW Skew between any 2 outputs 200 400 ps
Vin I Minimum Input Voltage @ 150 MHz(1) 20 10 mVPP
Vin II Minimum Input Voltage @ 250 MHz(1) 40 20 mVPP
VCM Input Common Mode Range -2.0 +3.0 V
fmax Max. Clock Frequency 500 550 MHz
Size 1.3 x 2.9 x 3.9 in.
Weight, w/o AC adapter 7 Oz
Shipping weight, w/AC adapter 4 lb

(1) If the switch is set to the center position (0 V threshold) a non-driven channel will oscillate and induce jitter in the driven channel. Connect any output to any input to stop the oscillation.

(2) 10%-90% for RS-422.

While we believe these models to be accurate, no representations are made as to accuracy or suitability for any application: